Can lithium batteries be used with the back up engine start feature?

[Professor David]

Rv tech tells me my two new LiTime 100ah lithium batteries are NOT to be used with the back up starting feature/switch in case the coach battery is low on charge. Is this correct?? This rv tech doesn’t seem to know what he is doing. I’ve had trouble w him getting the conversion to actually work. Ready to ask for a refund and take it someplace else.

 

[IBTripping]

A lithium battery doesn't have as much cold cranking amps as a lead acid start battery. However, I don't see any reason to not use them for occasional starting.

 

[CharlesinGA]

The backup start function depends on the charge/boost relay that interconnects the engine and house systems. Many times this relay is removed or disabled to prevent the engine alternator from being overloaded by the lithium battery. When the relay is removed or disabled, a battery to battery charger is used to provide a limited and regulated charge to the house battery. The problem is, this also eliminates the boost or "jump start" feature that depends on this relay being operational.

Charles

 

[DonTom]

The backup start function depends on the charge/boost relay that interconnects the engine and house systems. Many times this relay is removed or disabled to prevent the engine alternator from being overloaded by the lithium battery. When the relay is removed or disabled, a battery to battery charger is used to provide a limited and regulated charge to the house battery. The problem is, this also eliminates the boost or "jump start" feature that depends on this relay being operational.

Charles

The way I did both of my motorhomes is to use this DC2DCC to my added lith batteries. It limits the current to 30 amps max.

However, it breaks the path to use the backup battery switch. But in my Y2K motorhome, I also have my old roof solar reconfigured to keep my engine battery charged (I now only use external solar for the house battery) and also added a battery maintainer to the engine battery, so it stays fully charged whenever I have AC (genny or shore power). And I replace the engine battery every five years, so any problem is unlikely. Besides, I can restore the old path in a half hour if I need to and then use the backup switch by removing the DC2DCC.

In both my motorhomes, anything possible charges all the batteries, such as solar, driving, shorepower genny, etc.

-Don- Reno, NV

 

[Heli_av8tor]

I too disabled the control circuit to the combiner solenoid and put a 50 amp dc-dc charger to charge my lithium battery bank from the alternator.

However, I also designed a circuit to use the aux start boost switch to give me a jump if my chassis battery is low. When the switch is pushed the dc-dc is taken out of the circuit and the combiner solenoid is activated to connect the house and chassis battery banks together.

The proper way to use the boost is to hold the switch down for a minute to allow the house bank to put some charge in the chassis bank before engaging the starter, just like you would do with jumper cables. Don’t push the switch and instantly engage the starter.

 

[Mark_K5LXP]

It depends a lot on how the BMS for these batteries is set up with regard to overcurrent, how they're cabled (current balance), and the actual starting current needed (say 500cid V8 vs 300cid V6). Because there are a number of combinations that result in you being an unhappy camper the general advice is to say you can't. If you have knowledge otherwise (measured or empirical results) then full steam ahead. Otherwise consider it an experiment that could result in losing the boost feature.

Mark B.
Albuquerque, NM

 

[Lou Schneider]

A pair of Lion Safari 100 a/h lithium batteries had no trouble starting my motorhome's 7.4L Chevrolet V-8 via the boost switch when my Optima starting battery decided to disconnect itself (internal open) in the middle of Nowhere, NV a couple of years back. Let me continue my trip until I got back to the land of cheap batteries (Walmart) instead of having to pay small town prices for it's replacement.

As far as needing a DC to DC converter, 200 a/h of lithium connected to via the stock boost/charge relay draws about 25 amps each from the Chevy's alternator. A 50 amp load is well within the alternator's capacity. Larger batteries will need some kind of charge current regulation, though.

 

[mevman]

I explored for many moons regarding switching the house to Lithium batteries. Considering that my coach starts the generator and the fact as your tech mentions that they can't be used for Aux Start I opted for lead acid batteries once again this time around.
Yes...I considered changing the gen start configuration etc but since my coach has worked the way it is for over 15years and the fact also that battery power is rarely needed much more than 24 hours I stayed with original.
Since I could by Sam's Club Duracell GC2's for just around $500 I stayed with them.

 

[Professor David]

We want to do more boondocking so lithium seemed the way to go since our previous lead acid batteries boiled over a few months back. However, I am having second thoughts. Almost 3 k into this, the shop i took the rig to, does not seem to know what they are doing. I did have them put in a dc to dc charger. I would like to have the boost charging feature for peace of mind. I’ll re-read some of the comments above so I can “ have my cake and eat it too.”…if possible.

The problem now is the rig is back in the shop again for several days with no call back to me. Last I picked it up from the shop, there was no shore power or generator power going to the lithium batteries…so they were not charging w ac power. The dc to dc charger was working fine to charge the lithium batteries when the engine was running.

 

[Adventurous Traveler]

The way I did both of my motorhomes is to use this DC2DCC to my added lith batteries. It limits the current to 30 amps max.

However, it breaks the path to use the backup battery switch. But in my Y2K motorhome, I also have my old roof solar reconfigured to keep my engine battery charged (I now only use external solar for the house battery) and also added a battery maintainer to the engine battery, so it stays fully charged whenever I have AC (genny or shore power). And I replace the engine battery every five years, so any problem is unlikely. Besides, I can restore the old path in a half hour if I need to and then use the backup switch by removing the DC2DCC.

In both my motorhomes, anything possible charges all the batteries, such as solar, driving, shorepower genny, etc.

-Don- Reno, NV

I have nothing against lithium, but for us electrical challenged there seems to be a helluva of a lot of wiggle room regarding what is the best lithium set up. Unless I w has the expertise to solve the equation on your needs and set up, there doesn't seem to be enough knowledgeable techs to help steer you in the right direction.

On another forum I asked about upgrading my 4 GC2s to lithium. 99% of the responses
Focused on the cost of 4 new GC2s, totallying 640A (160 x 4) vs a couple of 100A lithiums. Out of over 40 replies no one mentioned what's being discussed in this thread. And, when I posted that my older Magnum Inverter/ Charger/ Converter didn't support lithium and it would be expensive to replace, I got tons of replies telling me about this cheap over the counter lithium charger and the next, never addressing the convenience of a class A with a generator, auto transfer switch, battery booster like described in this thread or the other more challenging prospects of switching my system from lead acid to lithium.

I met a fellow at a bar in Lake Placid, NY last night with a 28 ft Airstream. His 2 deep cycle marine batteries popped out for good a couple of weeks back. Peter asked the shop to cost out what upgrading to lithium would cost him. His estimate, $6000..his .agent

Peter told

 

[CharlesinGA]

I have nothing against lithium, but for us electrical challenged there seems to be a helluva of a lot of wiggle room regarding what is the best lithium set up. Unless I w has the expertise to solve the equation on your needs and set up, there doesn't seem to be enough knowledgeable techs to help steer you in the right direction.

On another forum I asked about upgrading my 4 GC2s to lithium. 99% of the responses
Focused on the cost of 4 new GC2s, totallying 640A (160 x 4) vs a couple of 100A lithiums. Out of over 40 replies no one mentioned what's being discussed in this thread. And, when I posted that my older Magnum Inverter/ Charger/ Converter didn't support lithium and it would be expensive to replace, I got tons of replies telling me about this cheap over the counter lithium charger and the next, never addressing the convenience of a class A with a generator, auto transfer switch, battery booster like described in this thread or the other more challenging prospects of switching my system from lead acid to lithium.

I met a fellow at a bar in Lake Placid, NY last night with a 28 ft Airstream. His 2 deep cycle marine batteries popped out for good a couple of weeks back. Peter asked the shop to cost out what upgrading to lithium would cost him. His estimate, $6000..his .agent

Peter told

I've said it before, its not as simple as replacing the batteries. Its installing an entire system, charge, storage, monitoring, and inverter, to make everything function. This all requires proper connections (wire crimps, proper size copper straps to carry the current, proper fuse types, etc) to make all of this work. If you don't follow the "rules" and the "best practices" you will have an inferior or substandard system that may, or may not work properly.

I'm a minimalist at heart and while I like all kinds of gee whiz things, for RV'ing, I like to keep it simple. I will stick with my Onan 2500LP generator and the group 24 AGM deep cycle battery I have. If I do any long trips out west, I might get a portable 200 watt solar system and use it, but that will be the limit of what I do in with my little trailer.

Charles

 

[Professor David]

The switch to Li has not been without some issues but it seems that we have the bugs worked out...fingers crossed. Our two lead acid batteries, that were only two years old, boiled over back in June. After getting some really useful info from members on this forum...it seemed clear that we had some problem with our charging system...so just putting in two new lead acid batteries wasn't going to solve our electrical charging issue. We needed two new batteries (if we stuck with lead acid I would have gone with AGM's (more expensive) since I hate checking battery water levels) and probably a new converter and needed a good rv tech to look over the whole system. At this point, we decided to convert to Li. The rv tech found some damaged wiring (slightly melted...not a good thing to find but glad he found it...if you know what I mean) in the charging system once he got into it. The tech also beefed up wiring, added several new breakers for safety and we decided to upgrade to a dc to dc charger. If we would have just replaced the lead acid system, it would have cost about 1.5 K or so...maybe more with upgrading the breakers and such...with the high labor costs. With the Li conversion, we spent a total of about 3K. Since we want to spend more time at sites without hook ups, the idea of charging in half the time with twice the electrical use time...appeals to us greatly. Less time running the generator in peaceful settings...we don't have solar...yet. The Li batteries we bought have bluetooth connectivity to monitor the batteries with a variety of very useful parameters in addition to state of charge. I also bought a portable battery booster which will replace the boost function on the motorhome lost with the conversion. Having a portable battery booster will also help in case we need it for our tow vehicle. With all that said, we are optimistic regarding the conversion.

 

[Lou Schneider]

I took the minimalistic approach, directly swapping in two Lion Safari 100 a/h lithium batteries to replace the same number of 12 volt lead acid house batteries in my Safari Trek motorhome, then evaluating how it worked with the stock system before making any changes.

I measured the charging current from the engine alternator using a clamp-on DC ammeter. It averaged 25 amps per battery, or 50 amps for both of them. 14 volts from the alternator filled them to better than 90% so I decided both of these parameters were acceptable and didn't install a DC to DC converter or make any other modifications.

On my first trip out, my starting battery failed in the middle of nowhere - it developed an internal open to one of the battery posts so it was totally out of the circuit. The pair of Lion Safari batteries started the 7.4 liter main engine just fine via the Boost switch, allowing me to continue my trip until I could get to a Walmart to buy a new battery instead of having to pay small town prices for the replacement.

 

[FunSteak]

I explored for many moons regarding switching the house to Lithium batteries. Considering that my coach starts the generator and the fact as your tech mentions that they can't be used for Aux Start I opted for lead acid batteries once again this time around.
Yes...I considered changing the gen start configuration etc but since my coach has worked the way it is for over 15years and the fact also that battery power is rarely needed much more than 24 hours I stayed with original.
Since I could by Sam's Club Duracell GC2's for just around $500 I stayed with them.

Did your genny start with the house batteries?

That's how mine was configured, and was my only hesitation about switching to lithium. My genny is the standard Onan 4000. I couldn't find much documentation on startup current draw, but the batteries I chose can output 100A continuous each.

I decided to go for it. I wired the batts with a separate, equal length leads from each terminal to pos and neg bus bars, along with two equal length parallel connections. House pos and neg connect to their respective bus bars, giving me full capacity from both batteries through 0 AWG cables all around.

When completed, I opened my Victron monitoring app, held my breath and hit start on the generator. Draws no more than 132 A while cranking. Batteries handled it without any issue, and nothing got hot in the process. Slightly higher voltage seems to crank the genny a wee bit faster, but that could just be my perception.

 

[DonTom]

That's how mine was configured, and was my only hesitation about switching to lithium. My genny is the standard Onan 4000.

My Y2k genny is a Onan 4K, and I have a single 300 AH lith battery that the genny runs from. Genny starts up faster than ever before. The higher voltage helps. But perhaps it won't be nearly as good as lead acid when it's very cold. IOW, there could be exceptions, but I wouldn't worry about it.

-Don- Auburn, CA

 

[Mark_K5LXP]

Onan 4000. I couldn't find much documentation on startup current draw

The Onan 4K is a 300cc engine. Think of it in motorcycle terms - a fairly lightweight bike. The Harley I have is 1340cc's- over 4 times larger, twice the cylinders and higher compression ratio. That bike starts with a lead acid battery that you can lift with one hand and fits in a happy meal box. Onan spec's a 360CCA battery for the 4K but it will draw nowhere near that amount of current when starting. I would guess less than 100A with a comfortable margin.

Mark B.
Albuquerque, NM

 

[RV_Lee122]

My rig sat in a park last summer for months and the chassis battery was super dead. I used the boost switch to get help from my 460Ah lithium and it did nothing. I don't know if thats because the chassis battery was toast, if the lithium couldn't do it OR if the boost switch was disconnected when the lithium and dc to dc were installed

It starts the generator no problem

 

[DonTom]

dc to dc were installed

That was why the boost didn't work. It breaks the path going back to the engine battery.

I have the same setup in my Y2K RV. I simply keep the engine battery well-charged and change it every 5 years. I just changed mine yesterday, getting it ready for some boondocking.

I added a 2-amp battery maintainer in mine so the engine battery will stay fully charged via the generator or when I have shore power.

-Don- Auburn, CA

 

[RV_Lee122]

That was why the boost didn't work. It breaks the path going back to the engine battery.

I have the same setup in my Y2K RV. I simply keep the engine battery well-charged and change it every 5 years. I just changed mine yesterday, getting it ready for some boondocking.

I added a 2-amp battery maintainer in mine so the engine battery will stay fully charged via the generator or when I have shore power.

-Don- Auburn, CA

Good to know, thank you!

Chassis battery is new last year so it'll be good for awhile. If I put it in a park next summer I'll just disconnect it. The one that went dead last summer was the original battery.