Charging an ebike from a leisure battery?

[DBrown67]

I'm going camping in September to the New Forest. Planning on going for 5 nights when I visit the autojumble and will be staying on a site with no electric hook up. Although I'm not new to camping I am a noob when it comes to leisure batteries, ebikes, solar panels etc.

I want to be as self sufficient as possible. On a previous trip I just got the staff at Beaulieu to charge my bike while I went round the jumble. That was nice of them and I could ask landlords in the pubs during the evening. But the plan is to consider around an 85ah lesiure battery with a 10W solar panel to trickle charge during the day while I'm out and about, and an inverter so I can use the 2 amp charger I got with my ebike kit.

So over to the more knowledgeable guys here... is this viable? Is a 10W panel enough?

There is no heating or lighting. Lighting is taken care of with rechargeable LEDs which won't run out for this length of trip. I do have a smart phone which will need charging a few times I would imagine.

My ebike battery is a 17ah 36V HL type battery. I don't envisage running it flat but you never know.

There is a 12V water pump for a shower with draw 6 amps. Can't see that running for more than 30 minutes in a day.

I also have a 12V TV/DVD player which can be plugged into 12 socket or plug into standard 3 pin socket. This might get used a couple of hours a day. And I understand it's best to not go below 0% of the battery capacity.
So looking at around 40ah to work with.

No fridge.

I know inverters are inefficient... but how much so? If I put 10ah into my ebike battery how many amp hours will draw from my leisure battery?

I can get a battery, inverter and 10W solar panel from Go Outdoors for about £140. Will this be good enough or will I just be frustrated?

 

[sjpt]

You don't mention the voltage on the leisure battery or the solar panel. If they're 12v then you'll need at least 30ah from the leisure battery for 10ah on the bike battery; I don't know about the efficiency but I guess you'll probably need more than 40ah.
Sorry, my mind wandered, you did say 10w, not 10amp on the charger. As Oscid pointed out, you won't get far towards keeping the bike going with a 10 watt panel; but if the leisure battery is 12v it should give most of a bike charge.

 

[Ocsid]

On exceptionally good days a 10 Watt will get 6 hours of high yield, so that will give you at best, 60 Watt hours of energy. [You will be off cycling or otherwise not there to optimise tracking the sun.]

Your 17 Ah 36 volt battery at best stores 17x 36= 612 watts hours.
So with 100% efficient charging, the best you can get will be one tenth of your e bikes battery's range, per day.
But of course, the charging to the leisure battery, inversion and charging of the ebike all come with losses. Let's assume overall 70%, so look more at achieving 7 % of the battery's maximum range per day.

You can play with differing "assumed" numbers, but not change the outcome very much.

I can get 100 miles from a full battery, in flattish terrain like much of the NF, so my battery gets me the 20 odd miles average per day, a 4 night weekend offers, without chasing recharges.

IMO the 10 Watt panel is massively undersized, if you really want on site , off hookup, recharging, I would go 80 to 100 Watts as some days it might not be overly sunny.

 

[GSV3MiaC]

Seconded.. A 10w panel is really a toy, which can keep your leisure battery sort of topped up when the boat / caravan / whatever is sat idle for weeks or months, or if you just run a led bulb or two. Won't even power a tablet or smartphone, much less charge a depleted leisure battery.

The leisure battery at 12*85 watt hours (and the 85 is slightly imaginary) holds not much more power than your bike battery, and weighs a lot more. Even a 100w panel (pretty large) will not recharge it in an average uk day.. You might be better off just taking a spare bike battery.

 

[DBrown67]

OK thanks guys. Looks like I'm wasting my time looking at this then. 100W panels run to about £300 or thereabouts from what I've seen. So if I get pubs etc. to allow me to plug in on an evening for the ebike then for the phone, shower and DVD player I might as well just use the car battery.

I'm averaging 35 miles on a full charge with my kit. Ofc I can get a bit more lowering the assist level.

 

[Ocsid]

OK thanks guys. Looks like I'm wasting my time looking at this then. 100W panels run to about £300 or thereabouts from what I've seen.

Something like this kit makes a bit of sense.

An evening in the pub probably more.

If you are camping near, the Carpenter's Arms at Bransgore do excellent meals with homemade pies, enough energy in those to pedal unassisted a fair way over the Forest.

 

[Tony1951]

If you are camping near, the Carpenter's Arms at Bransgore do excellent meals with homemade pies, enough energy in those to pedal unassisted a fair way over the Forest.

Now that's the kind of 'recharging' I like the sound of....

 

[mike killay]

I have recharged my 14 amp hours, 36 volt battery from my 90 amp hours 12 volt leisure battery using an inverter.
It worked but just about flattened the leisure battery, which I recharged by driving the campervan for a few hours.
I do not have a solar panel, TV or fridge to worry about, just LED lights and a water pump. I also recharge my phone and vapes off the leisure battery.

 

[Ocsid]

I have recharged my 14 amp hours, 36 volt battery from my 90 amp hours 12 volt leisure battery using an inverter.
It worked but just about flattened the leisure battery, which I recharged by driving the campervan for a few hours.

Again, no great surprise it is all about "energy", your 90 Ah battery holds, well did when the factory tested a sample, 1080 Watt hour, and typically can offer about half of that before getting into seriously damaging territory. [A few years in and probably holding just a fraction of its once capacity]
To fully recharge your bike battery, took more than 504 Watt hour plus the inverter and lithium charger losses, so way more out of the leisure battery than it ought to give.

The solution IMO for viable non damaging e bike recharging when camping off hook up, has to be a little top up but often so the leisure battery does not suffer too much abuse.

As has been said, and here it is important to realise, our bike batteries take much the same energy as our single lead acid leisure batteries hold, so a big recharging is never going to be viable. We can't really odds that with LA leisure batteries, as unlike lithium options the recharge rate, even if available can't be applied to a LA battery.

A good argument for taking that lingering meal, coffee or drink, leaving your mains charger quietly doing it stuff, if your ebike usage, requires it.

The amount of energy an ebike battery needs is large in respect to what we typically have in our leisure batteries, but trivial as an ask from a say a coffee shop, half a mains electrical energy unit, less than a £0.10 p ask even if flat and you are there 4 hours or more.

 

[mike killay]

Again, no great surprise it is all about "energy", your 90 Ah battery holds, well did when the factory tested a sample, 1080 Watt hour, and typically can offer about half of that before getting into seriously damaging territory. [A few years in and probably holding just a fraction of its once capacity]
To fully recharge your bike battery, took more than 504 Watt hour plus the inverter and lithium charger losses, so way more out of the leisure battery than it ought to give.

The solution IMO for viable non damaging e bike recharging when camping off hook up, has to be a little top up but often so the leisure battery does not suffer too much abuse.

As has been said, and here it is important to realise, our bike batteries take much the same energy as our single lead acid leisure batteries hold, so a big recharging is never going to be viable. We can't really odds that with LA leisure batteries, as unlike lithium options the recharge rate, even if available can't be applied to a LA battery.

A good argument for taking that lingering meal, coffee or drink, leaving your mains charger quietly doing it stuff, if your ebike usage, requires it.

The amount of energy an ebike battery needs is large in respect to what we typically have in our leisure batteries, but trivial as an ask from a say a coffee shop, half a mains electrical energy unit, less than a £0.10 p ask even if flat and you are there 4 hours or more.

I know that the literature recommends no more than 50% discharge for lead acid batteries, but mine are Rita batteries and can be discharged to 10.5 volts.
Also modern LA is a lot better than you seem to think. The 9 year old batteries on my electric boat are still giving at least 90% of new.

 

[RetiredAndRolling]

Hi. If you do go for a larger solar panel may I offer some advice? For use on a boat I purchased a weather-proof 120W folding panel. It worked well and did not take up too much room. However the moment it arrived I was surprised how heavy it was. Rigid panels, which are considered to last much longer than flexible panels, are heavy. The weight is not a problem for transportation but the effort to lift them from their storage area and open them is off-putting.

Fortunately I was able to get a second weather-proof 120W folding panel. It is made of flexible panels bonded onto a strong but light backing. It’s ace and I use it loads. The panel charges a 110Ah lead acid battery. Even with our rubbish climate it has no problem running a compressor fridge 24*7 when we are out. My battery meter usually shows hardly any charge going into the battery as by the time I glance at the meter the panel has already charged the battery in the very early morning sunlight.

So a lightweight high power panel can work well. Of course you'll also need a security cable to stop your gear being stolen. All-in-all not cheap but very effective and most pleasing.