Charging Lithium Batteries with Alternator

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Debra17

Debra17

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I have been researching how to set up a lithium battery system to be charged by the engine alternator. We are considering a 300AH lithium battery. As I understand it, a DC to DC charger should be used with a battery over 100AH. Looking at the cost of these components, I wonder if it is even necessary to have the alternator charge the coach batteries. We will have a MPPT charger to charge from the solar panels, as well as an inverter/charger that will charge from the generator. Adding another charge controller seems redundant and expensive. The only disadvantage of not having this functionality that I can think of is the battery boost function won't work. But there are other means available to replace this feature.

I also came across this video from Victron Energy which raises safety concerns.


Please educate me if I am missing something here.

Thanks
Debra
 
Debra17 said:
I have been researching how to set up a lithium battery system to be charged by the engine alternator. We are considering a 300AH lithium battery.
Click to expand...
I have a 300AH lith in my Y2K RV and since the battery voltage is normally higher than the alternator rectified & regulated DC voltage, it simply won't ever charge all the way to full while driving.

The lith battery cannot draw any current from the alternator when the voltage is as high or higher than the DC charging voltage from the rectified & regulated alternator, and will not draw much as long as it is close, even when the lith battery is a bit below what the charging can do.

I really couldn't understand what the guy was saying in the video, too much of an accent and my computer speakers here are not the best. And my hearing isn't all that good in my old age.

But I cannot see the lith battery drawing a whole lot of current unless it is very discharged, which will probably never happen in my case.

FWIW, I could very easy disconnect my lith battery while I drive if I think it is discharged enough to draw a lot of current--or simply run the generator to put a much higher voltage on the lith battery as I drive.

In my new RV, I did this, it will NOT charge from the alternator. I just don't see it as an issue either way.

So blowing out the alternator just ain't going to happen in my case. I just won't let the lith voltage get so low that it draws a lot of current from the alternator. I will either disconnect (wait to have shore power) or run the genny if it ever gets that low. Most likely, I will just run the genny to get the lith voltage up to a safe level, as I will want it to charge back up.

-Don- Auburn, CA
 
Thanks for those comments. I also thought of the possibility of a manual disconnect on the battery to alternator connection if some some reason we did want to charge off the alternator or needed the battery boost function to start the chassis battery.

We are looking at getting the same battery you installed. From the date of the photos, the install is pretty recent so I guess you don't have much experience with it yet.
 
Debra17 said:
From the date of the photos, the install is pretty recent so I guess you don't have much experience with it yet.
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In my new RV it is very recent. Recently purchased that RV. But the new RV will never be charging from the alternator at all.

My old RV it's been in there for a while. I find I rarely even run the genny in it anymore. Most of it's use is just to run it once a month or so to dry out the internal genny stuff.

I use the MW oven fairly oven while stopped for a lunch break. It's not good for the genny just to run it for a few minutes and shut it off. I can run the MW longer than I will ever need without using the genny--in either of my RVs.

For just me, 300AH of lith is overkill. But I like to have a bit more than I will ever need.

-Don- Auburn, CA
 
DonTom said:
In my new RV it is very recent. Recently purchased that RV. But the new RV will never be charging from the alternator at all.

My old RV it's been in there for a while. I find I rarely even run the genny in it anymore. Most of it's use is just to run it once a month or so to dry out the internal genny stuff.

I use the MW oven fairly oven while stopped for a lunch break. It's not good for the genny just to run it for a few minutes and shut it off. I can run the MW longer than I will ever need without using the genny--in either of my RVs.

For just me, 300AH of lith is overkill. But I like to have a bit more than I will ever need.

-Don- Auburn, CA
Click to expand...
I agree on having a bit more. The system I had in my trailer was really overkill for me but in four years I never had a problem charging my batteries. I didn't own a generator. In that I had 4 Lifeline AGM 220Ah batteries. Going by the 50% guideline, I had 220Ah usable. We were planning on the 200Ah lithium but not sure that is enough for the 2 of us. Also my husband uses a CPAP, so we need to be able to power that nightly. Thus thinking of going to 300Ah.
 
The main issue I have with the Victron video above is the speeds they are running the alternator are too low. Typical installations have a 3 to 1 ratio between the engine pulley and the alternator pulley so the alternator is turning that much faster than the engine. They said a 1500 RPM alternator speed is "much faster than idle" but since a typical engine idles at 600-800 RPM, the stepup ratio means the alternator is turning 1800-2400 RPM. At the 1500 RPM alternator speed shown in the video, the internal cooling fan is moving much less air, so it's not surprising the alternator overheated.
 
Hi Debra, we have 210 Ahs of lithium in our motorhome. So far I have not added a DC to DC charger or modified anything connected with the alternator. What I do religiously is keep an eye on my Victron battery monitor. Unless it's not reading correctly, it rarely charges at a rate of more than 50 to 60 amps per hour when the engine is running. And then for only a few minutes until the charge rate drops into the 20 to 25 amp range. Not sure why it's not charging at a higher rate but am not concerned about that.

As far as using the generator to charge the batteries unless you have a converter or inverter charger that has a lithium profile, it will not fully charge your batteries. IIRC, a standard converter will get them to maybe 80%. That's important when considering your Ah needs. Our 2 batteries have been more than adequate for us based on the way we camp. Our big draw is our 12v refrigerator which probably uses from 50 to 60 Ahs a day. Next is my iMac computer which uses maybe 5 or 6 amps an hour. Most of our lighting is LED so very little draw there.

I'm still concerned about the alternator over heating issue so would like to hear what you and the others do. Like you, we have some solar with an MPPT controller which will help to top off the batteries if they're not too low. We also use our Honda 2000 from time to time and the big Onan genny when Maria uses the microwave. Either will bring the batteries to 80% in a few hours. With full sun, our 200 Ahs of solar will top them off by the time the sun goes down. If I increase the solar to 400 Ahs, I think I'd have enough to keep the batteries fully charged without the genny. Then all I'd need is a larger Inverter so Maria can run the microwave.
 
Lou Schneider said:
The main issue I have with the Victron video above is the speeds they are running the alternator are too low. Typical installations have a 3 to 1 ratio between the engine pulley and the alternator pulley so the alternator is turning that much faster than the engine. They said a 1500 RPM alternator speed is "much faster than idle" but since a typical engine idles at 600-800 RPM, the stepup ratio means the alternator is turning 1800-2400 RPM. At the 1500 RPM alternator speed shown in the video, the internal cooling fan is moving much less air, so it's not surprising the alternator overheated.
Click to expand...
Hi Lou,
I wondered if Victron may have set the test up to perhaps skew the results. :)
Thanks for adding this perspective.
 
garyb1st said:
Hi Debra, we have 210 Ahs of lithium in our motorhome. So far I have not added a DC to DC charger or modified anything connected with the alternator. What I do religiously is keep an eye on my Victron battery monitor. Unless it's not reading correctly, it rarely charges at a rate of more than 50 to 60 amps per hour when the engine is running. And then for only a few minutes until the charge rate drops into the 20 to 25 amp range. Not sure why it's not charging at a higher rate but am not concerned about that.

As far as using the generator to charge the batteries unless you have a converter or inverter charger that has a lithium profile, it will not fully charge your batteries. IIRC, a standard converter will get them to maybe 80%. That's important when considering your Ah needs. Our 2 batteries have been more than adequate for us based on the way we camp. Our big draw is our 12v refrigerator which probably uses from 50 to 60 Ahs a day. Next is my iMac computer which uses maybe 5 or 6 amps an hour. Most of our lighting is LED so very little draw there.

I'm still concerned about the alternator over heating issue so would like to hear what you and the others do. Like you, we have some solar with an MPPT controller which will help to top off the batteries if they're not too low. We also use our Honda 2000 from time to time and the big Onan genny when Maria uses the microwave. Either will bring the batteries to 80% in a few hours. With full sun, our 200 Ahs of solar will top them off by the time the sun goes down. If I increase the solar to 400 Ahs, I think I'd have enough to keep the batteries fully charged without the genny. Then all I'd need is a larger Inverter so Maria can run the microwave.
Click to expand...
Hi Gary,
Thanks for the info on your system and the results you have had. I was so spoiled with the over sized system I had on my little trailer - I would go for days without looking at the battery monitor! I can't see myself religiously keeping an eye on how it was charging from the alternator :) So my thought right now is not to charge the battery from the alternator. I may have the connector that DonTom linked to above installed. Then if I did want to connect the battery it would be a simple matter.

I have been working with a dealer on getting a system designed. The initial proposal I received includes a Victron Energy Multi plus 12/2000/80 inverter /charger (2000 watt pure sign wave with 80 amp, which does have a lithium profile. The details on the components are in this post if of interest: Proposed solar system

I have been researching this inverter/charger this evening and I'm not sure it will work with the battery we are looking at getting, which is the Ampere Time 300Ah Plus. The Victron seems to be designed to work primarily with Victron batteries, which seems to be the case with their components. I'm reading the setup manual which states the battery needs to have a 2 signal BMS. Maybe that is standard, I don't know. I will need to contact the mfg to find out and if so get the required settings from them. Although I may look at other brands of inverter/chargers also. The other issue with this Victron unit is it doesn't have a low temp disconnect. The Victron charge controller that is proposed does have this setting. So maybe that is enough and it isn't necessary for the inverter/charger to have it. But it seems like it should.

I have been studying this stuff for a few days now and my head is about to bust. When I get one thing figured out then something else pops up!!!

The other option I have is to upgrade the converter. The existing converter is a Progressive Dynamics 9245. It can be replaced with a PD9145 ALV which is a multi-stage lithium charger. The drawback is it is still only 45 amps. And it doesn't have low temp disconnect.
 
Cold temperature charging protection is in the battery BMS (internal to the battery), not in the charging source. The battery will stop accepting a charge when it's internal temperature drops below OC (32F) but will continue to deliver stored power down to -20C (-28F).

You may be overthinking this whole converter/charger issue. Solar will provide most of your charging - the converter only comes into play when you are on shore power or when you run the generator. Even then, it only makes up any solar deficit.

If the Victron is too pricey, you could get just a regular inverter and let the solar and your existing converter handle the charging.

Your present 9245 converter IS multistage and while lithium doesn't need multistage, it will work well. It has the Charge Wizard logic built in and goes into Boost Mode (14.4 volts) for 4 hours when powered up, or you can select it manually with the external pendant. This is close enough to lithium's maximum 14.6 volts charging voltage.

It's fine when the converter voltage drops back to 13.6 volts. you can either boost it manually or let it ride. At that voltage the converter will either stop contributing to the charge if solar is providing enough power or charge the battery more slowly if there's a solar deficit.

The PD9145 ALV is a single stage charger with a constant 14.6 volts output. It's not enough of an improvement to worry about replacing your 9245 converter, IMO.

Here's a description of how the Charge Wizard works. Since the logic is built into your 9245 converter, you'd use the 92001 Remote Pendant instead.

Charge Wizard, 4-Stage Battery Charging System

Charge Wizard PD92201 Remote Pendant
 
Thanks Lou! I will look at the links. I guess I got the two confused.

I believe the Ampere Time/Chins batteries both have the low temp disconnect feature. However it was turned off at some point because it also turned off discharging of the battery which resulted in lots of complaints. I learned this as I was reading through all the customer questions on tha Amazon page for Chins. They supposedly had removed all references to it but may have missed some. It seems the BMS board could be modified though so that function could be turned back on. I may email them and ask about it.
 
Debra17 said:
The existing converter is a Progressive Dynamics 9245. It can be replaced with a PD9145 ALV which is a multi-stage lithium charger. The drawback is it is still only 45 amps. And it doesn't have low temp disconnect.
Click to expand...
I changed the 45 amp PD9245 converter in my Y2k RV with an 80 amp lith converter.

All you have to do is make sure your converter wires to the battery are not for only for 45 amps (8 AWG ) max. You could have to change those wires to something thicker to the battery, such as 6 or 4 AWG. My old RV had 6 AWG, which I left as is, but it is for a little less than 80 amps. But that is an continuous rating for the wire and an 80 amp converter won't often be charging at the full 80 amps, so the 6 AWG should be okay, which could be what you already have, so check that. I would change it if you have 8 AWG. Anything thicker (lower AWG number), I would just simply put an 80 amp lith converter in there, simple swap.

The AWG number is normally printed right on the wire's jacket (insulation) every few inches or so.

-Don- Auburn, CA
 
This morning I looked for the converter. It is in a compartment under the 2 drawers that are under the refrigerator and the pantry. It would be accessible by taking out one or both of the drawers. I didn't take them out to examine it further but will do so later (we are dealing with another repair right now that is a priority).

The remote pendant is supposed to be included with the converter. I haven't seen it in any of our manual cases or elsewhere. So I thought perhaps it is plugged into the converter already. I will check that and also the wire size out to the battery. Considering the inaccessibility of the converter, I don't think the pendant would be useful on a regular basis. It would be handy to verify that the converter is operating in the various stages I suppose.
 
Lou Schneider said:
The main issue I have with the Victron video
Click to expand...
Will that Victron DC2DC thingy raise the charge voltage enough to fully charge a lith battery while driving? If so, I could consider it, even though it probably isn't necessary.

And it could be an idea for my new RV as well, to charge my added lith while driving.

-Don- Auburn, CA
 
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