| Author | Message | ||
| les marston (Les_marston)
Registered Member Username: Les_marston Post Number: 56 Registered: 1-2010 Posted From: 24.70.15.101 Rating: N/A |
We are out in our little motor home... (Just till the 102 is done) and am having a problem with the 1750 watt inverter. We have 2 12 volt deep cycle batteries for the house and one regular battery for the start battery. charged thru a battery isolator Problem is that the house batteries are not charging or not charging enough to keep up with the inverter. We are not pulling a lot of 110 power. I guess about 3 amps when the fridge is running. No large draw items.We only use the inverter when we are traveling. Starting battery is charging at 14.2 volts but only 12.15 volts at the house batteries. Is this an isolator problem or are the house batteries just so low that the alternator cant put out enough to bring them back? We drove for 6 1/2 hours yesterday with no draw on the house batteries and they still are low. Is the alternator only "seeing" the start battery and not putting anything into the house battery? The batteries are all new as is the alternator. 90 amp alternator. Any ideas? Thanks Les | ||
| joe padberg (Joemc7ab)
Registered Member Username: Joemc7ab Post Number: 425 Registered: 6-2004 Posted From: 66.38.159.33 Rating: N/A |
Les House bat@ 12.1 would seem to indicate that it is not seeing any charge. I would try to bypass the isolator and hookup direct to your altenator to get some juice into your house batt. Gone how long? I will call when you are back. Joe. | ||
| les marston (Les_marston)
Registered Member Username: Les_marston Post Number: 57 Registered: 1-2010 Posted From: 24.70.15.101 Rating: N/A |
I think it is an isolator problem too Joe but I don't want to run out of starting battery. We are in Kelowna for a few more days then back to sunny Edmonton on the 30th. Les | ||
| Jim Wilke (Jim Bob) (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 490 Registered: 2-2001 Posted From: 12.107.194.78 Rating: N/A |
It is normal for an isolator to drop about 1 volt. The chassis battery is what the chassis alternator "sees" as it charges. Maybe a relay engaged by the vehicle "ignition" terminal would let you charge all of the batteries as you drive but drop out when you shut the engine off. | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1024 Registered: 8-2006 Posted From: 99.29.76.171 Rating: N/A |
Splitting some hair here, silicon semi-conductor material causes a 0.6 Volt drop. As the isolator uses two diodes, the drop across the house battery side is the same as the chassis side. Since the regulator sees the output of the alternator after the isolator, it automatically makes up for the .6V loss. Your isolator has one bad side, unless a cable is off somewhere. Quick and easy way to check, with the engine running, read the voltage between the alternator terminal, and the chassis batt terminal. It should read 0.6. Alt to house side SHOULD read 0.6 also, but if it has failed open, it will read 14... G | ||
| les marston (Les_marston)
Registered Member Username: Les_marston Post Number: 58 Registered: 1-2010 Posted From: 24.70.15.101 Rating: N/A |
Long and short of it is, The isolator is hooped. Any better way to separate the two batteries? Will a simple solenoid do the job and still charge the more depleted house batteries when the starting battery is at full charged? and will it handle the 90 amps that the alternator is rated for? Les | ||
| Jim Wilke (Jim Bob) (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 491 Registered: 2-2001 Posted From: 12.107.194.77 Rating: N/A |
George the alternator sees the voltage at the back of the alternator. If the chassis battery is before the isolator (as it was probably built) then it will charge properly and the house battery will be less, but I agree that it should not be more than 1 volt max. But answering Les's question, I would use a relay. Cole Hersee makes one that looks like a starter relay that is good for about 300 amps intermittant and the coil is rated continuous duty. This may still allow some uneven charging if one battery is older or weaker than another but it shouldn't be a problem as long as all are serviceable. Another solution would be to use gel cell batteries for the house batteries as they need lower charging voltage anyway. | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 269 Registered: 1-2007 Posted From: 208.81.157.234  Rating: N/A |
Do you have a set of jumper cables that will reach from start to house batteries? Attach them when the engine is running and remove when not. Keep an eye on the start battery to see if it is overcharging. (hot or boiling) Should get you home. Good luck Don Evans | ||
| les marston (Les_marston)
Registered Member Username: Les_marston Post Number: 59 Registered: 1-2010 Posted From: 24.70.15.101 Rating: |
got er figured guys. thanks for the help Les | ||
| Roderick W. Chandler (Rod)
Registered Member Username: Rod Post Number: 46 Registered: 11-2003 Posted From: 173.184.52.227 Rating: |
So what was the fix??? | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1025 Registered: 8-2006 Posted From: 99.172.181.44 Rating: N/A |
Jim, The ALTERENATOR sees the voltage at its output terminal, but the REGULATOR sees the voltage at the ignition switch, which is past the separator. So, the regulator compensates for the loss across the diode. As there are two diodes in an isolator in parallel, the voltage drop is the same across both of them, so both the chassis and the house batteries charge equally. If a one wire alternator is used, BOTH batteries will charge at 0.6 less than the internal regulator setting. G | ||
| les marston (Les_marston)
Registered Member Username: Les_marston Post Number: 60 Registered: 1-2010 Posted From: 68.151.225.213 Rating: N/A |
Well Rod, it is like this.... Made sure I had shore power each night and will put in a solenoid when I get home. This old motor home has a lot of sins from the PO I think it will take some time and chasing to get all of the bugs out. I have found that the built in 12 volt DC power supply only charges house batteries at 5 amps but it never stops, so if you leave the motor home plugged in for an extended time you cook the house batteries. I really hate putting time and money into this old unit because each dollar spent on it is one less for the coach. Toni insists that I fix it up because the coach won't be ready for about 5 years and we want to be able to take trips in the mean time. Thanks again guys for the help! It made it easy for me to decide what I would do to overcome this problem Les |
