95 Bounder: Had to replace the alternator last year. Now, the coach batteries only charge at about 10 amps, when they used to charge at about 45 amps. Did I get a "standard" alternator rather than heavy duty? It starts to charge at 45 amps, but immediately clicks off (I hear a clicking in the fuse panel). When on the road it took over 3 hours to replace 60 AH. I'm an Engineer, but this one has me stumped. Any ideas? Thanks in advance for info.
Charging Coach Batteries
- Thread starter pmscas
- Start date
The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
John From Detroit
Well-known member
That is one posibility, The other is that the battery is a bit more charged and thus won't accept the higher charge rate.
Alas, I do know the alternator "size" is stamped upon the alternator.. Where, I don't know. But it is there.
Alas, I do know the alternator "size" is stamped upon the alternator.. Where, I don't know. But it is there.
Gary RV_Wizard
Site Team
When you say "coach batteries", do you mean the chassis (engine start) batteries or the house batteries?
Assuming it is the house batteries, I'm guessing your coach has a pair of 6V "golf cart" batteries with a combined capacity of about 220 amp-hours. The max charge rate for a battery bank that size would be about20 11 amps (what they call the C/20 rate, i.e. capacity divided by 20 = charge rate), so I'm thinking your electrical system is regulating the charge down to around that rate (60 ah in 3 hours).
Where and how are you measuring the charging amps? Have you installed a shunt and a amp meter in the charge line from the alternator to monitor it or maybe using a clamp-type DC ammeter?
[edit]I fixed an arithmetic error - the C/20 rate for a 220 AH battery bank is 11 amps, not 20[/edit]
Assuming it is the house batteries, I'm guessing your coach has a pair of 6V "golf cart" batteries with a combined capacity of about 220 amp-hours. The max charge rate for a battery bank that size would be about
Where and how are you measuring the charging amps? Have you installed a shunt and a amp meter in the charge line from the alternator to monitor it or maybe using a clamp-type DC ammeter?
[edit]I fixed an arithmetic error - the C/20 rate for a 220 AH battery bank is 11 amps, not 20[/edit]
Yes, they are golf cart house batteries. I'm measuring the charge on a shunt ammeter between battery and ground. When dry camping I run the engine every 3 days or so to restore the charge. Prior to the alternator change I could restore about half of the charge in an hour or so. Thanks for the assist.
Gary RV_Wizard
Site Team
Interesting that the old alt charged that fast. It is true that a severely drained battery will accept a high rate for a short time and 30-40 a-h in the first hour is doable. Would not continue that fast, in my opinion. Is it possible that your batteries are well charged and simply not accepting more than around 10A? Have you run the batteries way down and then tried a measurement?
By the way, my arithmetic was faulty in the previous post - the C/20 rate for a 220 a-h battery bank is 11A, not 20A [220/20 = 11].
By the way, my arithmetic was faulty in the previous post - the C/20 rate for a 220 a-h battery bank is 11A, not 20A [220/20 = 11].
Lou Schneider
Site Team
- Joined
- Mar 14, 2005
- Posts
- 13,328
I suspect the clicking you hear in the fuse panel is an automatic resetting circuit breaker interrupting and restoring the battery charging circuit. It might be the new alternator is more potent than the old one - where the old one charged at a lower rate that didn't trip the circuit breaker while the new one supplies more current but is being constantly interrupted.
Gary RV_Wizard
Site Team
Good thought, Lou. My previous rig had a 50A breaker in the charge controller circuit. After I upgraded the charger from 50A to 90A, that breaker would open if I ran the batteries down too low and then started charging. A PITA, since it was not an auto-reset breaker. I finally put a manual bypass on so I could charge for a few minutes without resetting the breaker a dozen times. After a few minutes of charging, the rate dropped low enough that I could open the bypass switch and the breaker would hold.
