solar powered SLA charging?

[needWheels]

I've seen solar trickle chargers for car batteries, it is possible to (cheaply) modify or (easily) make from scratch an SLA charger for an ebike that won't be used everyday, so therefore could charge on alternate days?

(By the way, what does it technically cost to recharge a 24-36 volt SLA setup, I've saw someone say 10 cents, is that accurate?)

Thanks!

ps. I'm an electronics novice though I can use a soldering iron in general

 

[TylerDurden]

Howdy,

Can be done. Let's say one round-trip per day, just for example.

Ya gotta calculate your needed power: you might use 480wh each RT. (WAG)

You might get 4hrs good sun each day, so you divide the needed power by 4 = 120w/h.

Harbor Freight has 45W systems for ~$200; you'd need three, = $600

You could have two packs: one charges while the other is in use.


Using the grid to charge is cheap. 7kWh costs me less than a buck.

 

[safe]

SLA Needs To Be Worked

The problem with trickle charging an Electric Vehicle is that when you do deep discharges it exposes the SLA cells to sulfation. In order to break off the sulfation you need to really bang hard at the cells with high amps and ideally some shaking. (AC or square wave)

So it's not a good mix.

You really need to charge up a capacitor with the solar power and then "pulse" the energy in so that you can shake up the cell. Pulsing is better than trickling for SLA.

 

[needWheels]

Very interesting and helpful info, many thanks.

Would a NiCd or NiMh charge more easily from solar?
Could they in theory trickle charge from nine hours of daylight?
It seems very wasteful in efficiency but if special rates/methods are needed I guess a solar panel could drive an inverter to use the regular 110v charger?

$600 is way outside of my budget (more than I am putting into my first ebike!) so it will have to wait. The $25 solar trickle chargers just had me thinking. Thanks for filling in the blanks.

 

[safe]

Would a NiCd or NiMh charge more easily from solar?

NiCad and NiMh have their own problems. They tend to not send a clear signal to say that they are charged full if you trickle charge them. Solar power can be uneven (a cloud can block the sun) and that will wreck havoc on the charging algorithm.

LiFePO4 seems like a better possibility and it's lighter weight too, but it's also the most expensive.

I've forgotten the website, but there is a place that sells SLA chargers for solar that do this pulse charging technique. It can be done... but you also would have to pay for it.

The biggest problem is that even these little ebikes demand huge amounts of wattage compared to what a small solar panel can provide. You would need a lot of surface area to get any reasonable charge.

The bottom line is that it doesn't really work very well.

(better to charge from solar panels attached to your home because they can be big enough to do what you need)

 

[TylerDurden]

Let's confuse the issue with facts:

The charge current for small lead-acid batteries should be set between 10% and 30% of the rated capacity (30% of a 2Ah battery would be 600mA). Larger batteries, such as those used in the automotive industry, are generally charged at lower current ratings. Cells constructed of a non-antimonial lead grid material allow higher charge currents but have a lower capacity. The cylindrical Cyclone is sealed and can sustain a pressure of up to 3.5 Bar (50 psi). A pressurized cell assists in the recombination of gases.

Observe the battery temperature, voltage and current during charge. Charge only at ambient temperatures and in a ventilated room. Once the battery is fully charged and the current has dropped to 3% of the rated current, the charge is completed. A good car battery will drop to about 40mA when fully charged; a bad battery may not fall below 100mA.

After full charge, remove the battery from the charger. If float charge is needed for operational readiness, lower the charge voltage to about 13.50V (2.25V/cell). Most chargers perform this function automatically. The float charge can be applied for an unlimited time.

http://batteryuniversity.com/partone-13.htm

PV modules output ~15V (12V nominal)... 2-module pairs would be used to charge a 24V ebike... each pair provides 1.875A... 3 pairs would be 5.625A.

Most ebike SLA chargers are between 1.5 and 5 amps.

As per B.U. above, if you have a pair of 20Ah SLAs, charging at a rate of 20% capacity would be 4A.

No problem for solar there.

If you had half the PV modules, you could charge @2.5A for two days.

(You can only count on about 4hrs useful sunlight, unless you live in a southwest desert.)

 

[safe]

Caution

A warning to you as a new person... TylerDurden is somewhat of a "rogue charactor" on this forum. The advice he's giving is in contradiction to all the evidence found over time by people using them for EV's. If you do not use a desulfating charger with SLA your cycle life will fall significantly. SLA can only be expected to last 300 cycles anyway and of you failed to use a desulfating charger that might drop to 150 cycles. Many solar systems try to keep their batteries at near full charge and so it's a different situation than the deep discharges of EV's.

Just be careful... :wink: (a word to the wise)

 

[safe]

http://www.batterystuff.com/solar-chargers/SP-5.html

This would be more like what you need. You could probably have one of these and when you park your bike someplace it could just pulse charge a little. Then you could have a separate standard charger for overnight for the bulk charge.

At $159 it's not cheap though...

 

[TylerDurden]

You can see the current ratings of many e-bike chargers here:

http://tncscooters.com/partsdb.php?type=ES

 

[safe]

You can see the current ratings of many e-bike chargers here

But those are crap. That's the whole point... anyone that charges their SLA batteries without desulfation is lacking in knowledge about the issue.

 

[TylerDurden]

Much has been said about pulse charging lead-acid batteries. Some experts believe there is a benefit in reduced cell corrosion but manufacturers and service technicians are not in full agreement on the effectiveness. There are also disagreements on the 'equalizing charge'. An equalizing charge raises the battery voltage for several hours above that specified by the manufacturer. Although beneficial in reversing sulfation, the side effects are elevated temperature, gassing and loss of electrolyte if the service is not administered correctly. A periodic discharge of about 10% is said to benefit the battery but little conclusive evidence is available.

http://batteryuniversity.com/partone-13.htm

 

[safe]

A Compromise?

I've found on my own bike that if I occasionally do a 10 amp desulfation routine every once and a while it really wakes up my cells and makes them work better. This is in contrast to the charging rate I use of 3 amps for the main charge. This is on big 38Ah cells.

What could work is to use a solar trickle charger during the day when your bike is parked somewhere. (where it can't get stolen ) Then at night you hit the cells with the desulfation hard for a little while to clean everything out. You don't need to always desulfate, but if you never desulfate and also do deep disharges it's bad news.

Much of the quotes from Battery University are generic and don't always take into account the specific tweeks that EV's use, so you have to adjust your thinking to the actual stuff you are working on.

Trust me... you NEED desulfation or your cycle life will suffer...

 

[TylerDurden]

Caution

A warning to you as a new person... TylerDurden is somewhat of a "rogue charactor" on this forum. The advice he's giving is in contradiction to all the evidence found over time by people using them for EV's. If you do not use a desulfating charger with SLA your cycle life will fall significantly. SLA can only be expected to last 300 cycles anyway and of you failed to use a desulfating charger that might drop to 150 cycles. Many solar systems try to keep their batteries at near full charge and so it's a different situation than the deep discharges of EV's.

Just be careful... :wink: (a word to the wise)

I just debunk BS from posers.


If you consider offsetting the cost of gasoline, the amortization rate of PV systems for an EV gets much better. I use my EV's for trips to the home-depot, grocery store, visiting, etc., etc.

 

[safe]

I just debunk BS from posers.

So tell us about all the projects you've been working on?

Aren't posers people that don't actually build anything?

(a black man calling the black pot black?)

And I can probably figure why you have problems with SLA... if you are using one of those chargers that don't desulfate you KNOW that your cycle life will be reduced.

In the time I've been here and learning all the tricks of this game you seem to be stuck... like you haven't progressed at all... it seems to me that you need to start something new.

Time to go forward... get out of the rut... start a new project...

 

[vanilla ice]

You guys need to get a room..

 

[safe]

You guys need to get a room..

We're working towards some possible software upgrades that might be able to filter this sort thing out, but for now it's something that's dragging the forum down. I'm sorry it's come to this.

 

[Dr. Shock]

What you need is a charge controller and a solar panel (obviously). Charge controllers can be very cheap and low power or sophisticated and high power. Look at Xantrex model c12, which will take about 200 watts and do more than you need. You can charge an ebike easily with a 50 watt panel and a small charge controller. To keep costs down, you'd probably charge the batteries in parallel at 12 volts instead of 36v in series. Lots of charge controllers on ebay.

 

[needWheels]

Thanks for all the solar info. I see the conflict but I am used to arguments on other kinds of forums so I can deal with it. I realize everyone has their own opinion on things and I can respect that.

Solar apparently will have to wait if it's going to be in the $200+ class though. I was thinking there might be a way to do it cheap enough to pay for itself in a year but if it's only going to cost a quarter to charge off the grid, I'll make do with that for now.

I actually own a car-battery/SLA desulfation charger made by schumacher which is one of those $50 walmart specials. Never have seen the desulfate circuit kick in though, my UPS batteries are always too far gone to recover and there apparently is no way to force it on, it has to decide for itself.

Using SLA's on an ebike might be the first time I get to see it do something useful (haven't had a working car in a year!)

Didn't occur to me that I might be able to charge the SLAs in parallel at 12v though, might work since this charger has a high amp setting and supposedly intelligent to not over-charge.

 

[safe]

I use one of these:

...and charge in 12 volt parallel. It works great. The desulfation does it's little routine at the beginning and then it "beeps" and then full power charges then "beeps" then taper charges then "beeps" and finally trickle charges.

However... to get that last bit of charge at the end I do individual cells one at a time using the same charger to "top off" each cell. I've got a weird configuration right now where there's a mix of old and new SLA's so they all need individual attention. The new one's can go a couple extra minutes compared to the older one's.

If you want to save money and already own something like mine then just use it, you will be okay.

 

[needWheels]

Safe, I have one of these http://www.amazon.com/dp/B000FH9ONC (but paid far less)
The manual says this:

DESULFATION MODE: If a battery is left discharged for an extended period, it could become sulfated and not accept a normal charge. If the charger detects a sulfated battery, the charger will switch to a special mode of operation designed for such batteries. Activation of the special desulfation mode is indicated by blinking the CHARGING LED. If successful, normal charging will resume after the battery is desulfated. The CHARGING LED will then stop blinking and light continuously. Desulfation could take up to 10 hours. If desulfation fails, charging will be aborted and the digital display will blink

I figured I would always own a used car so a decent charger was a good idea.
Then I ended up with no car at all because it didn't make sense for less than 10 miles roundtrip.
(But I am starting to miss the places on the other side of town that are 6+ miles uphill all the way hence the ebike project - taking a bus for an hour gives me a migraine)

By the way, where is a good place to get decent (but low cost) cables to connect SLA batteries so I can switch them from serial to parallel easily?

 

[safe]

By the way, where is a good place to get decent (but low cost) cables to connect SLA batteries so I can switch them from serial to parallel easily?

I went to ACE hardware and bought thick wire... really thick. Then you need to cut it and solder it together in the right way. You need some connectors and the two most people use are either:

Deans Connectors
Anderson Powerpole Connectors

...I have experience with the Deans and they work well and people I've heard from also like their Andersons so either way is fine.

Just keep in mind that the thicker the wire the LOWER the waste in terms of resistance. Don't go cheap with thin wire because it really will heat up. My first wiring harness needed replacement because it was too thin. You need something like 14 gauge to 10 gauge wire. (I might be wrong on that, but I'm pretty sure those are the numbers) As I recall 16 gauge (thinner) was what I had that failed.

http://www.rbeelectronics.com/wtable.htm

10 gauge is difficult to work with, so 14 gauge is easier.

 

[TylerDurden]

You can use thin wire in pairs to do the same as thick wire. More flexible.