Batteries and their technologies, Which is best ?

[magnetman]

Oddly that came up as a quote from @canalboat77 when it was actually me who posted it. 

 

Good point about the size of bank.

 

For the brew I think perhaps best to stick with gas. If it is commercial production of tea making water it is a different kettle of fish. 

 

Engine running most of the time to me equals one really good quality AGM battery about the size of the alternator. 

 

I'm no pro though. 

 

Just like smaller battery banks and efficiency if possible. 

[canalboat77]

2 minutes ago, magnetman said:

Oddly that came up as a quote from @canalboat77 when it was actually me who posted it. 

 

Good point about the size of bank.

 

For the brew I think perhaps best to stick with gas. If it is commercial production of tea making water it is a different kettle of fish. 

 

Engine running most of the time to me equals one really good quality AGM battery about the size of the alternator. 

 

I'm no pro though. 

 

Just like smaller battery banks and efficiency if possible. 

 

We make about 60 pots of tea over two trips a day - so we do need a lot. We use propane gas for the tea/coffee, and a calorifier for the hot taps for washing up etc. 

[BEngo]

3 minutes ago, Alan de Enfield said:

Using your engine to generate electricity to heat water is madness. It cost ~£5 per Kw* you can, plug into the 'mains' and its ~30p, even using your gas heater will be far cheaper than your engine.

 

This is entirely true as a stand-alone activity. It is marginally true if the engine is already at work propelling the boat.  Lets  consider a 1,5 kW kettle.  Given an adequate alternator, wiring etc   so that the battery is only acting as a buffer, not a power source, the kettle will increase the load on the engine by 2HP, plus the additional alternator   and wiring losses.  Say 3 HP in total for a wildly inefficient set up.  The engine will already be producing  say 10 HP, so we have a 30% increase in demand, and,  crudely, in costs.  I would guess electric is now about £1 a unit.

 

Still dearer than a solar panel,  probably cheaper than Hinckley Point C.  Mains  electric is hard to get when you are going along though.

 

For boiling a kettle for tea,  the answer is not a gas water heater as it won't get the water hot enough.  A kettle on the gas is probably good for one or two, but for a boat load of passengers the answer is probably a zip boiler on an electric set up designed to manage it.

 

N

[magnetman]

4 minutes ago, BEngo said:

 

This is entirely true as a stand-alone activity. It is marginally true if the engine is already at work propelling the boat.  Lets  consider a 1,5 kW kettle.  Given an adequate alternator, wiring etc   so that the battery is only acting as a buffer, not a power source, the kettle will increase the load on the engine by 2HP, plus the additional alternator   and wiring losses.  Say 3 HP in total for a wildly inefficient set up.  The engine will already be producing  say 10 HP, so we have a 30% increase in demand, and,  crudely, in costs.  I would guess electric is now about £1 a unit.

 

Still dearer than a solar panel,  probably cheaper than Hinckley Point C.  Mains  electric is hard to get when you are going along though.

 

For boiling a kettle for tea,  the answer is not a gas water heater as it won't get the water hot enough.  A kettle on the gas is probably good for one or two, but for a boat load of passengers the answer is probably a zip boiler on an electric set up designed to manage it.

 

N

 

It will be a commercial boiler not a water heater. 

 

One wonders at this stage if it would be wise to consider doing beer instead of tea. Refrigeration seems easier to sort out than boiling water. 

[Tacet]

3 hours ago, nicknorman said:

I did mention alternator controller. It has a fast/slow charge switch. On slow, field current is limited to about 1/2 such that the 170A alternator produces about 75A at idle and 95A at canal cruising speeds. The alternator temperature is around 60C which is quite cool.

 

If I put the switch to fast, maximum field current is authorised until the alternator temperature gets to 90C, then it’s reduced to hold the temperature around 90C. Long term this gives around 125A. At engine rpms below about 1300, maximum field current is reduced until it’s back to 1/2 at idle. This stops the engine struggling with a big load at low rpm, excessive belt load/pulley side force etc.

 

This same fast/slow switch also puts the Combi into fast charge mode so if the travelpower is on, I get another 60A or so from the Combi.

Hmmm.  I get that, but if the principal benefit of lithium batteries is to recharge in a shorter period, then the alternator needs to work harder.

 

I suppose with your variable knob you can reduce the max current and (probably) still decrease the overall recharge time in order to be kind to the alternator, but you might need to think ahead on the expected running/cruising time.

[nicknorman]

35 minutes ago, Tacet said:

Hmmm.  I get that, but if the principal benefit of lithium batteries is to recharge in a shorter period, then the alternator needs to work harder.

 

I suppose with your variable knob you can reduce the max current and (probably) still decrease the overall recharge time in order to be kind to the alternator, but you might need to think ahead on the expected running/cruising time.

 

Not really. The principal benefit - or benefits - of lithium batteries are that it recharges at a uniform and potentially very fast rate, and that there is no need to fully charge - in fact it is better not to fully charge. In our case it is 15% per hour at slow charge rate (we have 600Ah). Doesn't matter if that is taking it from 20% to 35%, or from 80% to 95%, the charge rate is the same.

 

With LA, the alternator works very hard for the first few minutes and then the current tapers off, and then it spends the next many hours tapering off more and more until the current finally reaches say 1% of capacity indicating fully charged after at least 8 hours. The average charge current over the 8 hours is very low. And it is necessary to repeat this quite often, at least once a week.

 

With Li the charge current (at the sorts of partial C we use in boats) remains fixed at a potentially high value until the batteries are very nearly fully charged. As I mentioned I can put in about 90A steadily, so for an average usage of say 135 Ah per day, that is around 1.5 hours charging. Day after day. Lots of people manage on a lot less than 135Ah per day. Especially as 135 Ah of Li is worth more than 135Ah of LA.

 

If and when you do want to fully charge (eg to synchronise the BMV once a month) then the 90A continues to go into the batteries until about 5 mins before they become fully charged - the current tapers off really quickly. OK particularly quickly because the alternator voltage regulation on our alternator controller is very precise, but even with a conventional linear regulator it will still be a much, much quicker taper than for LA.

 

Practically speaking Li can be charged as fast as you like, the trade off is in alternator life and while one can take steps to improve things (better alternator cooling) I think being able to put a day's worth of charge back in in 1.5 hrs (or just over 1 hr if I use fast charge mode at 90C alternator temperature) day after day is pretty good and not worth working on improving.

Edited April 25, 2023 by nicknorman