Battery recharging-Old Motorhome
- Thread starter SierraTom
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Kirk
Senior Member
Re: Battery recharging-Old Motorhome
When you operate an RV with power supplied from either a generator or from shore power it supplies the batteries by the same 120V/12V converter that supplies the lights and appliances. Since these converters are usually sized such that they have limited current capacity there is only a small amount of current left to charge your coach batteries. In addition, the converters are normally set to supply a constant voltage of about 13.5V and charging a battery at a high charge rate requires 14-14.5V, that too limits the charge rate and means that it will take a very long time to restore your batteries to near full charge. In addition, the typical RV converter will never completely charge a battery to full capacity because of the voltage limits.
Quality battery chargers or the alternator of the chassis engine have a voltage regulator which increases the output voltage to keep the charge rate high until charged and it then lowers that voltage to about 13.6V, which is the proper resting voltage for a wet cell battery when fully charged. RV converter are mostly of designs that are cheap and which have little or no regulation and only a single voltage ouput.
The best answer to recharging your coach batteries from your generator is to buy a quality, three stage battery charger at an auto supply store or Wal-Mart and use that, plugged into one of your 120V outlet This will recharge your batteries at a much faster rate and it will do a much better job of charging them as well. You will have a higher charge level and your batteries will last longer.
When you operate an RV with power supplied from either a generator or from shore power it supplies the batteries by the same 120V/12V converter that supplies the lights and appliances. Since these converters are usually sized such that they have limited current capacity there is only a small amount of current left to charge your coach batteries. In addition, the converters are normally set to supply a constant voltage of about 13.5V and charging a battery at a high charge rate requires 14-14.5V, that too limits the charge rate and means that it will take a very long time to restore your batteries to near full charge. In addition, the typical RV converter will never completely charge a battery to full capacity because of the voltage limits.
Quality battery chargers or the alternator of the chassis engine have a voltage regulator which increases the output voltage to keep the charge rate high until charged and it then lowers that voltage to about 13.6V, which is the proper resting voltage for a wet cell battery when fully charged. RV converter are mostly of designs that are cheap and which have little or no regulation and only a single voltage ouput.
The best answer to recharging your coach batteries from your generator is to buy a quality, three stage battery charger at an auto supply store or Wal-Mart and use that, plugged into one of your 120V outlet This will recharge your batteries at a much faster rate and it will do a much better job of charging them as well. You will have a higher charge level and your batteries will last longer.
Re: Battery recharging-Old Motorhome
Thank you folks for your reply... you've given me some ideas to explore.
I am most curious about this three stage charger... never heard of that before and Wal-Mart is just down the road.
I'll discuss with my friendly auto mechanic ( not an RV expert) .... there has to be a better way to have 2 new baterries not go dead in the middle of a 25 degree night in the Sierras.... ( I'll assume the heater drained the batteries to zilch)
Thank you folks for your reply... you've given me some ideas to explore.
I am most curious about this three stage charger... never heard of that before and Wal-Mart is just down the road.
I'll discuss with my friendly auto mechanic ( not an RV expert) .... there has to be a better way to have 2 new baterries not go dead in the middle of a 25 degree night in the Sierras.... ( I'll assume the heater drained the batteries to zilch)
Kirk
Senior Member
Re: Battery recharging-Old Motorhome
Tom, unless your friendly mechanic happens to be an RV owner I very much doubt that he knows much about them. In general, the chassis engine's alternator is a much better means of charging the coach batteries than is the on-board generator set if you depend upon the converter to do the charging. Typical charge times using the converter for two coach batteries are eight to ten hours or more. With the chassis engine running at a high idle, say with a brick or such on the accelerator, the charge time will be more on the order of an hour or so per battery.
I agree that the coach batteries could be part of the problem, but even with the very best deep cycle batteries, you still will not get them to charge from the generator-set in less than 8 to 10 hours because the converter supplies too little current and at too low a voltage.
Tom, unless your friendly mechanic happens to be an RV owner I very much doubt that he knows much about them. In general, the chassis engine's alternator is a much better means of charging the coach batteries than is the on-board generator set if you depend upon the converter to do the charging. Typical charge times using the converter for two coach batteries are eight to ten hours or more. With the chassis engine running at a high idle, say with a brick or such on the accelerator, the charge time will be more on the order of an hour or so per battery.
I agree that the coach batteries could be part of the problem, but even with the very best deep cycle batteries, you still will not get them to charge from the generator-set in less than 8 to 10 hours because the converter supplies too little current and at too low a voltage.
Re: Battery recharging-Old Motorhome
Just replaced my batteries also. They were about 7 yrs old. I tried testing with a hydrometer (sp) and got inconsistant readings, and the battery guy said they they can't always be trusted either. On the posts of my batteries is stamped the date of mfg.
Just replaced my batteries also. They were about 7 yrs old. I tried testing with a hydrometer (sp) and got inconsistant readings, and the battery guy said they they can't always be trusted either. On the posts of my batteries is stamped the date of mfg.
Re: Battery recharging-Old Motorhome
I don't understand why the heater may have drained the batteries??? Batteries may run the circuit board for the furnace, fridge, lights but that should not have drained them completely unless (1) they are extremely old, (2) you were not running the generator while using stuff, or (3) your converter is not charging when the generator is running or your on shore power. you did not say whether they worked fine shore power?? Good Luck
I don't understand why the heater may have drained the batteries??? Batteries may run the circuit board for the furnace, fridge, lights but that should not have drained them completely unless (1) they are extremely old, (2) you were not running the generator while using stuff, or (3) your converter is not charging when the generator is running or your on shore power. you did not say whether they worked fine shore power?? Good Luck
H2H1
Senior Member
Re: Battery recharging-Old Motorhome
WELL ARCHER and SCOOTER I had to replace my house batteries while out in SD. I t is now in the shop (4 weeks now) the main ECB the big black box under the hood had to be replaced. I sincerely hope that is not your problem. It took 2.5 weeks to get from Fleetwood since they have filed for bankrupt. I did get it but what a hassle. Now the jacks have to be repaired, the valve assembly has to be replaced, Boy it keeps plying up. I be glad when it stops, I need to go camping and not worry about what it is going to cost or what it cost.
WELL ARCHER and SCOOTER I had to replace my house batteries while out in SD. I t is now in the shop (4 weeks now) the main ECB the big black box under the hood had to be replaced. I sincerely hope that is not your problem. It took 2.5 weeks to get from Fleetwood since they have filed for bankrupt. I did get it but what a hassle. Now the jacks have to be repaired, the valve assembly has to be replaced, Boy it keeps plying up. I be glad when it stops, I need to go camping and not worry about what it is going to cost or what it cost.
C Nash
Senior Member
Re: Battery recharging-Old Motorhome
Well I did see where Toms post did say the batteries are new. Missed that at first. Think he was just thinking the gen would charge faster but one hour running will no where near recharge them to full.
Replaced both my house batteries yesterday. Now guess I'll be down with the back again. Them buggers are heavy. Hollis not going to tell you what my son got them for. Man what a mark up.
Well I did see where Toms post did say the batteries are new. Missed that at first. Think he was just thinking the gen would charge faster but one hour running will no where near recharge them to full.
Replaced both my house batteries yesterday. Now guess I'll be down with the back again. Them buggers are heavy. Hollis not going to tell you what my son got them for. Man what a mark up.
RE: Battery recharging-Old Motorhome
My experience has been similar. I found that with the generator running there is only a trickle charge (12.85) going into the house battery. Certainly not enough to charge it. I purchased a Battery Minder Plus which I plug into my outside outlet. I run the generator for an hour or so and the Battery Minder Plus is putting about 13.8+.
That charges the battery. I run the generator usually during breakfast in the morning for an hour or so and then I do the same thing during dinner in the evening. It also keeps my battery charged and "conditioned" while I am not using the RV.
My experience has been similar. I found that with the generator running there is only a trickle charge (12.85) going into the house battery. Certainly not enough to charge it. I purchased a Battery Minder Plus which I plug into my outside outlet. I run the generator for an hour or so and the Battery Minder Plus is putting about 13.8+.
That charges the battery. I run the generator usually during breakfast in the morning for an hour or so and then I do the same thing during dinner in the evening. It also keeps my battery charged and "conditioned" while I am not using the RV.