Can I use jump leads to charge a flat leisure battery

mikeonb4c · Post by **mikeonb4c** » Sun Sep 09, 2007 11:26 pm

I've got the 'corblimey' setup for my leisure battery i.e. the Voltage Sensing Relay wont handle high currents so is protect by a 25 Amp fuse. This means if the leisure battery goes flat and then tries to draw a massive current through the relay on starting up, the fuse blows to protect the VSR.

Well I flattened my battery recently and thats exactly what happened. However, I didnt discover it until a week later. When I did, I had no option but to recharge using my mains battery charger (and even that kept switching on and off for the first 15 mins to protect itself). I've got 2 questions:

1) What could I fit as a simple means of knowing that the leisure battery is flat and not receiving charge due to a blow fuse

2) If this happened away from being able to mains charge, would it be safe to put jump leads across from the starter battery to charge the leisure battery at least for a bit until it does not draw a current such as to blow the 25 amp fuse. Also, if it is OK, should I hold back from attaching the jump leads until after I've started the engine. Also, is there a danger that the leisure battery may damage itself by receiving charge at too high a current? Is there a danger the alternator may be upset at having to deliver a charging current that high?

Grateful for any advice the BF leccies might be able to give. Could be of general interest to others with the 'corblimey' system

Thanks chums

Mike

daveblueozzie · Post by **daveblueozzie** » Mon Sep 10, 2007 12:05 am

can only answer question one Mike ,i fitted a simple volt meter on top of the battery with i think something called a dead man switch ,so it only works drawing voltage when you push it.,so when i open the bonnet i can easily check its got a charge and also with engine running that it is getting a charge.cost about a tenner.hope this helps with part of your problem.

mikeonb4c · Post by **mikeonb4c** » Mon Sep 10, 2007 8:39 am

Oooh thats good Dave and I guess it could be dashboard mounted if wanted. Where did you get it - ebay?

thanks

Mike

mikeonb4c · Post by **mikeonb4c** » Mon Sep 10, 2007 8:53 am

What bout ones of these - item 150157014465 on ebay. As regards power consumption when Bongo is not in use, I was thinking of fitting a panel mounted switch to isolate the leisure batter from the 3 x ciggie lighter anyway as that has a light that draws power and is on all the time at present. If I put the voltmeter in the same switched circuit then it would only be on when the circuit is switched to on. I'm not a leccie though - anyone got any advice on that?

Mike

pippin · Post by **pippin** » Mon Sep 10, 2007 8:57 am

You can use a jump lead from the engine battery to the leisure battery.

It is exactly the same as jumping one vehicle from another.

You would need to have the engine running otherwise you could flatten the engine battery.

Connect the lead to the +ve of the leisure battery first.

Now, there might be one hoor of a spark as you connect up to the engine battery +ve, so don't be a chicken and dither about - be positive (!) about it and make a real firm first connection.

While it is being charged like that you can set about changing the fuse.

Then after a few minutes or so you can disconnect the jump lead, engine battery end first and the fuse should hold to continue the charging.

The usual disclaimers & etc about liability, coupled with the usual warnings about safety precautions.

mikeonb4c · Post by **mikeonb4c** » Mon Sep 10, 2007 12:54 pm

Excellent pippin & thanks. What amazes me is you'd think the leisure battery would do itself damage while receiving this kind of charge rate, but I guess that is what makes leisure battery design what it is.

I'll make sure I keep some jump leads stowed henceforth.

Whats you view on the voltmeter idea?

Mike

dp bradford · Post by **dp bradford** » Mon Sep 10, 2007 1:14 pm

Mike - I've got one of these, it can be used to see if the battery is getting a charge simply by reading the voltage, and you can compare the engine and leisure batteries at the flick of a switch. Not as cheap as your suggestion though

Dave

pippin · Post by **pippin** » Mon Sep 10, 2007 1:21 pm

I did in fact have a digital voltmeter that I could switch between the two batteries for that same info. Very Useful.

The Hymer Van has one buit in to the control panel.

Ralph · Post by **Ralph** » Mon Sep 10, 2007 3:56 pm

I have one of those battery condition indicators that
plug into the ciggy lighter just stick it in the one in the
back nr the side door it is powered by the leisure battery,
the leisure battery is in the back on mine as it as the two
vehicle battery's under the bonnet so due to the length of
the cable runs it never gets a absolutely full charge you
always loose a volt or two on a 12/14v system with long
or light duty cable runs.

Manny · Post by **Manny** » Mon Sep 10, 2007 5:01 pm

I also have had the leisure battery fuse blowing when the electric cool box has been on too long and discharged the battery flat. It happened when I was camping without a hook-up so could not use the battery charger. In my tool box I had some cable and some spare light bulbs. I started the engine and connected the leisure battery to the main battery using the cable in series with a 15 watts bulb, this will limit the charging current to just above one amp. The bulb lit up and I left it there for a few minutes until it went out ( the difference in batteries voltage was then too small to light the bulb). I then removed the cable and bulb and replaced the 25 amp fuse. I now carry a cable with croc clips and a spare bulb all the time in my tool box.
To check if the leisure battery is charging I use one of these http://www.maplin.co.uk/Search.aspx?cri ... ce=15&SD=Y I changed the terminals with a cigar socket plug which I connect to the cigar socket in the cab and I can check it whilst I'm driving. I have all the sockets connected to the leisure battery. When I have time ( don't hold your breath)I hope to make device using relays to insert a bulb in the charging circuit of the leisure battery when it detects the voltage is below 12 volts to prevent the fuse blowing.

Manny

mikeonb4c · Post by **mikeonb4c** » Mon Sep 10, 2007 5:40 pm

Excellent tips Ralph and Manny, I could even wire that into a 2-way switch as an over-ride for the fused relay circuit, Manny. The Zig think looks neat DP_ but what is the cost out of interest?

dp bradford · Post by **dp bradford** » Mon Sep 10, 2007 7:04 pm

mikeonb4c wrote:...The Zig think looks neat DP_ but what is the cost out of interest?

About 25 quid. As I say, not cheap - but it does exactly what it says on the tin! And it is neat

Dave

Jefferson · Post by **Jefferson** » Mon Sep 10, 2007 8:04 pm

Pippin commented and pointed out the need to be careful.

"

You can use a jump lead from the engine battery to the leisure battery. .........Now, there might be one hoor of a spark as you connect up to the engine battery +ve, so don't be a chicken and dither about - be positive (!) about it and make a real firm first connection."

I would like to emphasize this need to take care.

It's true the method will work but would stress the need for extreme caution if you decide to do this. Probably only in dire emergencies.
In a 'former life' i worked as an electrician/electrical engineer. Saw several colleagues badly hurt and scared by an exploding battery showering acid and debris around. If a battery is faulty, gassing or just flat a shower of sparks, or any heat source, may ignite the gas causing an explosion. In training Electricians and Motor Vehicle Mechanics these Health and Safety aspects are paramount.
Many's strategy for charging the Leisure battery seems a safer option to me.However in emergencies we sometimes have to weigh up the risk
If you do use 'jump leads' in this way try to protect your eyes and keep your face as far back as possible. Follow the procedures set down in the manual or as shown in this thread. They are designed to reduce 'flash over' as much as possible.
The key message is 'Take Care'.

We don't want to be reading about a collection of 'Fried Bongoliers' in the forum.

mikeonb4c · Post by **mikeonb4c** » Mon Sep 10, 2007 11:52 pm

Point taken Jefferson & thanks. Manny's solution would seem to provide a workaround so that I don't have to resort ot jump leads. I'll have a think about how to make his idea a permanent installation option.