is there any cheap alternative to a battery to battery charger ,im sure years ago i bought something to connect both batterys up that was very cheap i was abit surprised at how expensive the b to b chargers are any help appreciated.
b to b charger
- Thread starter gpz
- Start date
are you sure you mean a battery to battery charger or are you thinking of a battery master, the former is intended to charge the leisure batteries more efficiently and the latter is intended to keep the engine battery charged from the leisure battery.
Is this what you want?
OP
OP
what i have found with our new to us van which is a 1997 vw compass calypso is that to charge the leisure battery you need to conect up to hook up there does not seem to be any way to charge the leisure battery other than hook up i wanted some way for the alternator to charge the leisure battery i may be miss describing what i want electrics are a mystery to me
My poorly drawn diagram is for charging cab and leisure batteries from a solar panel
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OP
OP
any ideas where it may be jaws that would be great if that was the problem thanks again for your reply
I don't know the details of your motorhome, but in general it works like this. The split charge relay connects the leisure battery to the starter battery/alternator when the engine is running, and disconnects when the engine stops.
There will be a big fuse (30A, maybe 50A) in the wire from the starter battery, located very near the battery. There will be a similar fuse in the wire from the leisure battery, located very near the battery. These fuses can be corroded and so make a bad contact. Or they could be blown, obviously. These fuses are the first thing to check.
Most motorhomes, especially older ones, have a split charge relay. Motorhomes with a multiple leisure batteries, lithium batteries, or new motorhomes with smart alternators, might have a B2B charger instead of a split charge relay.
There will be a big fuse (30A, maybe 50A) in the wire from the starter battery, located very near the battery. There will be a similar fuse in the wire from the leisure battery, located very near the battery. These fuses can be corroded and so make a bad contact. Or they could be blown, obviously. These fuses are the first thing to check.
Most motorhomes, especially older ones, have a split charge relay. Motorhomes with a multiple leisure batteries, lithium batteries, or new motorhomes with smart alternators, might have a B2B charger instead of a split charge relay.
OP
OP
ok thanks for that the leisure battery is under the rear seating area there are 3 relays just next to the leisure batttery but how do i know which is for the split charging ? and will these be vw only or will i be able to pick one up from the local motorfactors or even off e bay all thought appreciated thanks again for all the comments and ideas it is really helpfull
Do you have a multimeter? This can be invaluable for tracing faults, etc.
Automotive relays are usually fairly standard. There are 4-pin and 5-pin types. The 5-pin has 4 pins exactly the same as the 4 pin, plus an extra pin.
A relay is an electrically operated switch. A small current through a coil causes a magnetic field, that pulls two heavy-duty contacts together. When the coil current stops, a spring pulls the heavy-duty contacts apart.
The leisure battery and starter battery will probably have slightly different resting voltages. At the split charge relay, one heavy-duty contact will be at the starter battery voltage, and the other will be at the leisure battery voltage. At other relays, such as the fridge relay, only one of the heavy-duty contacts will have a voltage on it.
The relay coils are activated by a thin wire from the alternator when it is up and running.This wire is usually called the D+ wire, and is a kind of 'engine running' signal.
One thing to watch out for is, converters sometimes fit a 'voltage-sensitive relay' (VSR) to work as a split charge relay. Instead of using the D+ wire, a VSR monitors the incoming voltage. If it is over a certain threshold, maybe 13.4V, the VSR assumes the alternator is charging the starter battery, and switches on the relay. When the engine stops, the battery voltage drops below the threshold, and the VSR turns off. A VSR has only 3 contacts, instead of 4 or 5 for a standard relay.
Automotive relays are usually fairly standard. There are 4-pin and 5-pin types. The 5-pin has 4 pins exactly the same as the 4 pin, plus an extra pin.
A relay is an electrically operated switch. A small current through a coil causes a magnetic field, that pulls two heavy-duty contacts together. When the coil current stops, a spring pulls the heavy-duty contacts apart.
The leisure battery and starter battery will probably have slightly different resting voltages. At the split charge relay, one heavy-duty contact will be at the starter battery voltage, and the other will be at the leisure battery voltage. At other relays, such as the fridge relay, only one of the heavy-duty contacts will have a voltage on it.
The relay coils are activated by a thin wire from the alternator when it is up and running.This wire is usually called the D+ wire, and is a kind of 'engine running' signal.
One thing to watch out for is, converters sometimes fit a 'voltage-sensitive relay' (VSR) to work as a split charge relay. Instead of using the D+ wire, a VSR monitors the incoming voltage. If it is over a certain threshold, maybe 13.4V, the VSR assumes the alternator is charging the starter battery, and switches on the relay. When the engine stops, the battery voltage drops below the threshold, and the VSR turns off. A VSR has only 3 contacts, instead of 4 or 5 for a standard relay.
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Last edited:
How to use a multimeter. If you're not familiar with using multimeters, there's a lot of help on here. For example, post 10 of this thread to get you started.
www.motorhomefun.co.uk
Then search for 'how to test a fuse' and 'how to test a 4-pin relay'
Leisure Battery Issues
Hi all, newbie here after picking up our 2007 Hymer B660 SL last week. I am having issues with the Leisure Battery and would appreciate anybody’s advice. Firstly we are really happy with the van, it is in great condition for its year and has lots of service history etc. However upon collecting...
www.motorhomefun.co.uk
I learnt how to use mine by watching YouTube
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