Monitoring leisure battery and split charge modification

[1664]

Yes, I know you can get an indication of the condition of your leisure or starter battery by measuring the voltage but wouldn't it be nice to also know what current your camper electrics were drawing from your leisure battery when you're camped up with the lights, TV and Propex running? And wouldn't it also be nice to know exactly how much current a heavily drained leisure battery was raping out of your alternator when you restart your van?

I fitted this while I was semi-sober at Angelseystock (picture quality reflects DT's)............

Current drain on battery when running internal lights, T.V and Propex (minus sign show current leaving battery rather than going in)



Partially discharged battery voltage



Battery voltage with engine started and alternator doing it's bit



and current being sucked from the alternator by a thirsty leisure battery due to watching too much South Park (note no minus sign so current going in)



and current from the alternator after a fair few minutes of engine running



Wiring at the battery and the 100 amp current shunt. No people, this is NOT the finished article, this is just to get it up and running and will be tidied up when I can be ar$ed to get around to it....



I have blown a few 50 amp fuses and at £5 a throw was getting a bit miffed The problem is that when you initially start up there is a sudden inrush current 'spike' into the leisure battery before it drops to it's steady charging current flow rate and this is what has been buggering my fuselinks. My split charge cable can take 70 amps but guess the next size fuse link up from 50 amp? 75 smeggin' amps that what!! To say I'm tempted is an understatment

The other thing about this is the accuracy in the low range – I checked the reading against two other ammeters I have and it's a bit iffy to say the least. I suppose asking a current shunt thats built to take 100 amps to be accurate in the 0-5 amp range is a bit optomistic so I've set it to be 'spot on' at about 5 amps. Total cost about twenty quid...................

[Titus A Duxass]

Please post more details of your monitor, I would like something similar.
I have a voltage monitor driven by a bar graph generator (LM3914).

[1664]

This is the digital display and shunt in one package - not same seller as I bought off but a lot cheaper (oh why oh why didn't I wait until a cheaper one turned up ) You can buy them seperately if you prefer

http://cgi.ebay.co.uk/3-DC-100A-Blue-LC ... 3a58dc95f2" onclick="window.open(this.href);return false;

[ringo]

Awesome Bren - love it.

Where is the 50A fuse that your blowing? Inline with the meter?

Ringo

[1664]

No it's either one of the split charge fuses mounted on the battery terminals themselves I showed you





The meter feed itself has a 2A in line fuse protecting it

[Titus A Duxass]

Cheers for the link.

[kevtherev]

That is just what I need....

thanks for sharing Bren

[Oldiebut goodie]

" have blown a few 50 amp fuses and at £5 a throw was getting a bit miffed The problem is that when you initially start up there is a sudden inrush current 'spike' into the leisure battery before it drops to it's steady charging current flow rate and this is what has been buggering my fuselinks. My split charge cable can take 70 amps but guess the next size fuse link up from 50 amp? 75 smeggin' amps that what!! To say I'm tempted is an understatment"

Now you can see why I recommend a 100A setup instead of the puny 30A Smartcom setup.
Why are you using such expensive fuses? The Durite ones can be picked up for £1.50 for 10.

[1664]

I feel that 100A is a bit OTT (each to their own; also I think my alternator's max output is 65A) and as I said the cable would take 70amp. I chose this type of fuse and fuse carrier because it mounts directly onto the battery terminal eliminating any unfused cable sections no matter how short. I also stumbled across this type of fuse after I had installed the wiring etc. A 60A fuse wouldn't have melted BTW - the inrush was 58A. Fuses vary considerably in how accurate they are and how forgiving they are with short term inrush - these are obviously pretty accurate and not very tolerant.
Once I discovered they didn't do 60A or 70A versions I decided to risk the 50A and to be honest they are fine 99% of the time (so I wasn't expecting to replace them) but if I over do the TV consumption when parked up for a couple of days it drags the battery right down. I'm probably going to fit another battery in tandem to be honest............ and I know the 70A rating of the cable errs on the side of safety so I'm going to investigate how much it can truly take and if it will take 75A then I'll get them instead.



Available from RS Components - I would post a link but they have 'improved' their website so now it doesn't work and I can't access the item(s)
Fuselink is item No 337-7915 which you can search for once they get their act together.

[Oldiebut goodie]

The 100A setup helps to keep voltage drop down as well as coping with the surge - gives your leisure battery the chance of maximum voltage.

I run a 180A setup on my Merc camper - but then I have two 110Ah leisure batteries that are nearly 20 feet from the engine and starter battery.

It isn't so much what the alternator puts out it's the current that will also flow from the starter when the split charge relay connects. People forget that this happens (or ignore the fact).

[ringo]

It isn't so much what the alternator puts out it's the current that will also flow from the starter when the split charge relay connects. People forget that this happens (or ignore the fact).

Why will the starter be on when the relay connects?

Ringo

[Oldiebut goodie]

With reference to the sentences above it - starter = starter battery. We are talking batteries here, not cream cakes, starter motors, spaghetti or whatever.

[ringo]

Calm down. I get it now.

Thanks for clarifying.

Ringo

[1664]

The 100A setup helps to keep voltage drop down as well as coping with the surge - gives your leisure battery the chance of maximum voltage.

I run a 180A setup on my Merc camper - but then I have two 110Ah leisure batteries that are nearly 20 feet from the engine and starter battery.

It isn't so much what the alternator puts out it's the current that will also flow from the starter when the split charge relay connects. People forget that this happens (or ignore the fact).

I can see why volt drop is an issue for you but frankly it's almost irrelevant with my set up (short runs) and the size of my cables (3.8mV/A/M).
Considering that my battery was discharged to the point that the propex wouldn't fire up and the inverter refused to function, the leisure battery was pulling just 48A (with admittedly a 58A initial surge) then my original 70A would have easily coped. I tried the 50A purely because of the lack of a 60A or 70A version of those fuses.
Yes I do know that a really flat battery will pull an amazing amount of current from the alternator (and the starter battery) but I've only ever inadvertently run one so flat that even the water pump wouldn't operate once, and then I just connected jump leads across to by pass the split charge system.
I'm not saying don't fit a 100A system if you want to - hell, fit 200A if you fancy it, the sky's the limit since a totally drained battery runs a close second to a short circuit. I'm just saying 70A is quite sufficient for quite heavy use and is certainy enough for me (although a second battery will be added as it's the capacity that lets my system down rather than the split charge).

Anyway, what do think of the meter??

[Oldiebut goodie]

It's amazing the 'cheap' electronic gadgets that you can get from the Far East nowadays. The only thing that I have found with them is you have to check the soldering - I have found poor joints on all sorts of stuff. I have used the separate versions when they first appeared.

Well done for taking the trouble to photograph what you have done.