Some battery questions!
Hi
I will be staying off grid for 4-6 nights and am very nervous about running out of battery!
I have just checked my Van and it has a NUMAX battery but I cannot see any indicator to capacity although I am sure I was told it was a 90Ah when I purchased the van (second hand).
It has never shown fully charged on the panel in the van so am considering changing it so here are my questions:-
1 - Is there any reason not to fit the largest Ah battery you can get? I have seen a 120Ah NUMAX exactly the same dimensions as my existing battery. Is there any reason not to fit this as a replacement?
2 - If I do get the 120Ah and the old one is 90Ah, is there any reason why I cannot connect them in parallel, as this should give me loads of capacity?
3 - It appears the old battery has two terminals for each of + and - I assume I can connect from the old battery to the empty connector on the replacement?
4- Really dumb question, if wiring in parallel negative to negative and positive to positive?
5 - If I do wire like this, will it cause my Sargent charger (solar panel) any issues?
6 - Can I use standard jumper cables or is there a spacial cable I should use?
7 - Anything I have forgotten to ask?
Many thanks for all the anticipated helpful answers!
Comments
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The biggest battery you can fit is always the best option.
They can technically be connected in parallel but will never charge correctly. Even two batterys of same size will have problems. This is because they will rarely have identical states of charge and will keep trying to charge each other. This can produce a lot of heat and two flat batterys.
If you were connecting in parallel it is plus to plus and negative to negative.
There are solar panel controllers on the market that charge, seperately, two battery, which can be of different sizes. This is your best option. Around £40 if I recall.
DO NOT USE JUMP LEADS. They will jump off at some point and cause a great hazard, even fire or explosion. Use proper battery clamp connectors - there are ones available that clamp with a lever action to allow quick release to change batterys.
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Blimey Rob you are worried.To cut your post down somewhat and to make it easier,is go for the best battery which you can afford we use 110amp and go for a solar panel.
I have a 55 watt solar but others on here use larger.We have been off grid for 6 days and did not suffer any battery issues but we did not use a tv.
Make sure you have enough gas and then you will see that you can manage without the orange lead.
Incidentally most vans have voltmeter displays,this should read around 12.8 on a fully charged battery.
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Regarding your batttery. I wouldn't connect it together with a new one as it sounds like it may be suspect. If you buy a new battery, then imho the heavier the battery is for a given Ah rating the better quality it is likelly to be. The NCC gives some batteries a rating
NCC verification . This might be a helpful guide.
You don't say what size your solar panel is but this time of year it doesn't need to be huge to keep up with sensible usage. For what is worth we were away without ehu this weekend and on Sunday by the time I had staggered up to make a coffee at 9 00 am the battery was showing it was fully charged. We hadn't used the TV but even if we had the panel would have coped. They just need a healthy battery to store the charge.
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Hi
Many thanks for the feedback.
My panel is an 80W unit.
I am considering either:-
NUMAX CXV35MF – 120AH DEEP CYCLE BATTERY
Or
ADVANCED XD35 DUAL PURPOSE LEISURE BATTERY
I cannot seem to find the NCC rating for these but they should do the job.
Any opinions?
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I use a 150w folding solar panel with a 110amp Numax battery, it was kept charged up for 12 nights last year and it will be for more nights this yea,r even using TV for 3-4hrs a night.
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Forget about running the two batteries in parallel for the reasons stated above PLUS the significant additional weight.
You don't say what van you have but unless it has the full Sargent system (smart charger) then you should always take the battery out after discharging and recharge using a decent leisure battery charger. Many vans just put 13.8 volts on the battery which is only good enough to maintain the charge, not to recharge.
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Swift Conquerer 630 (2010)
As far as I am aware it has a full Sargent smart charger built in.
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1 - Is there any reason not to fit the largest Ah battery you can get?
Yes, You must consider the following.
Space available
What proportion of your payload weight you wish to allocate to batteries.
The specification of your solar charge controller - some small charge controllers will not provide sufficient amperage during the charge phase to maintain a healthy battery over a certain size. This is of course less important if you are providing a maintenance charge from a different source when at home.
2 - If I do get the 120Ah and the old one is 90Ah, is there any reason why I cannot connect them in parallel, as this should give me loads of capacity?
NEVER DO THIS
You can wire two batteries in parallel but to ensure a balanced system you should only ever use 2 batteries identical in make, age and specification - preferably made at the same time, and on top of this be very careful about wiring them using identical cable lengths and resistance to your load. even minor differences in overall resistance can cause major differences in overall efficiency and longevity of the setup.
A reliable article can be found here How-to-connect-batteries-correctly.pdf
3~6 answered in the article above
7 - Anything I have forgotten to ask?
Yes
You have failed to tell us what you need the electricity for.
A 110Ah battery does not actually give you 110Ah (1.32kwh) of power, it should be able to give you half of this reliably. This is because discharging below 50% dramatically reduces the number of charge discharge cycles the battery is capable of.
A good article can be found here caring-for-and-charging-your-leisure-battery
Therefore: if the power is drawn over a period of 8+ hours. Therefore you should not really be loading more than 80 watts if you want the battery to last 8 hours.
A decent article can be seen here (written by the competition I'm afraid)
Looking after your leisure battery.
You should assume that your 80 watt panel will give you on average a top up of 13 amp hours a day. A bit less on very overcast days or after the autumn equinox, and conversely a little more on a sunny summer's day.
Based on a reasonable quality, fully charged and well maintained 110Ah deep cycle leisure battery... calculate what you think you will be using daily and deduct 13Ah from your daily consumption (what your panel feeds back into the system). This should give you an idea of how long the 55Ah of capacity in the battery will last you.
For a 5 day trip I suspect you should be aiming for a total maximum daily consumption of 24Ah (0.288kwh).Day 1 55Ah battery 13Ah solar 24Ah usage 44Ah reserve
Day 2 44Ah battery 13Ah solar 24Ah usage 33Ah reserve
Day 3 33Ah battery 13Ah solar 24Ah usage 22Ah reserve
Day 4 22Ah battery 13Ah solar 24Ah usage 11Ah reserve
Day 5 11Ah battery 13Ah solar 25Ah usage 0Ah reserve
I run on 2 x 110Ah deep cycle leisure batteries, have a 175w solar panel mounted on the roof, a decent charge controller, a decent quality pure sine wave inverter (600w). I frequently live off grid for 2~3 weeks at a time and have never gone home with less than 85% charge. I do limit consumption to a maximum of 50Ah (0.6kwh) a day. These loads are mostly charging and running laptops, a very little bit of TV, lights and electricity for other friend's devices. Very occasionally heating water midday for washing if there's a lot of sun and the batteries are already full.
I hope this helps
Mark
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Thanks 00mark, that is one hell of a comprehensive reply!
I have just wrestled my existing battery out of the van to see exactly what it is I have as I had been told it was a 90Ah.
In reality it turns out it is a 110Ah and was fitted in 04/14.
So I guess it should be good for what I need, at least I hope so!
I suppose I should have done this first but just went with what I had been told.
So last question.
How do I figure out the Ah usage to charge a couple of iPads, and a couple of iPhones?
Plus some lights and maybe a couple of hours of telly!
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iPad and phone chargers are usually 5 Watt (some are 10). 5 watts is less than half an amp so the power consumption is half an ampere hour per hour's use. Insignificant.
TV is the biggest power consumer so you need to work out the power consumption from the details on the TV or in the manual or check it online. I never use a TV away so cannot help but on this forum it has been said that some TVs can use 2 or 3 amps so if it is on for 2 hours that could be 4-6 Ahr.
Light bulbs can be large power consumers if they are the old fashioned halogen types but on modern vans they will be LEDs and use very little power.
Remember that you should plan to take not much more than half the capacity before the battery gets to the point where further discharge would damage it. So, say 60 Ahr. but you need to monitor the voltage to check the status.
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No worries,
OK energy consumption calculation 101
It's simple school maths
watts (P) = volts(v) x Amps (A)
Amps = Watts / volts
etc.
So let's look at a telly rated at 120 watts, 240 volts. that draws 0.5 amps (AT 240 VOLTS) we however are using an inverter to convert 12volts dc to 240 volts ac, that is a difference of 20 therefore the current that the inverter would be pulling from the battery would be 20 times higher.
120/240 = 0.5
0.5 x 20 = 10
the telly will be drawing 10 amps from the battery, and if it was on for 1 hour you would have consumed 10 amp hours. (I have deliberately not bothered with the losses in energy thanks to the inverter)
Makes sense?
lets look at an easier example...
A fluorescent light fitting uses 18 watts and runs on a 12 volt battery, it's current is 1.5 amps, if on for 1 hour draws 1.5Ah
Approx Ah of some stuff
TV Led mid size, 8 Ah
strip light 30cm 1.5 Ah
Ipad charger 1 Ah
Iphone charger 0.5 Ah
water pump 8 Ah
12volt fridge 10+ Ah
Car radio 1 Ah
so
2 Iphones charged for 1 hour a day,
2 Ipads charged for 1 hour a day,
3 lights on for 4 hours a day
30 minutes of pump for the sink and 2 x 7.5 minute showers
3 hours of TV
1 hour of radio.
phone 2 x 0.5 = 1
pad 2 x 1 = 2
light 3 x 4 x 1.5 = 18
pump (.5+.25) x 8 = 6
TV 3 x 8 = 24
Radio 1 x 1 = 1
Total of 52 Ah
less charge from solar (approx 13Ah ?)
used from battery 52 - 13 = 39Ah
Make a list of what you think you'll use like the above and make your own calculation.
A fully charged battery will show a stable no load reading of 12.7 volts a battery at around 50% will show 12.1 volts.
see table below
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What ever you do don't connect two dissimilar (either by Ah or age)batteries in any way at all, if nothing else your battery charger will not be happy. Get the biggest, by Ah and size, you budget and caravan will accept.
I have a 135Ah Banner Energy Bull along with a 100W solar panel. We recently did a week away (8 nights) completely off EHU and at the end the battery was just as charged as it was when we arrived.
Even your 80W panel should, over the course of the day (even if it's cloudy), recharge your battery of anything you should use during the evening (lights, TV, pump).
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