Modding charger with voltage tester

Flashlight Modding and DIY Parts
1

I have an xtar wp2 ii for my lithium batteries and was considering the vp1 but could not justify buying another charger just for the volt meter.

Is there a simple way to purchase a voltage tester and just modding it into the wp2? Can I just solder the wire’s onto the charging tabs or is that dangerous?

Maybe something like this:
http://www.fasttech.com/products/0/10002968/1222900-036-display-3-digit-3230v-voltage-tester-for-18650

Or maybe one that is better and can read lower voltages?

If there is no way, I guess I’ll just solder on some magnets and use the voltage tester as a independent unit. I basically just don’t want to have to take out my DMM every single time before and after a charge.

2

This has slightly better range i think

http://www.ebay.co.uk/itm/300885287429?ssPageName=STRK:MEWAX:IT&\_trksid=p3984.m1438.l2649

I have it hooked up to a xtar MP1

Or you could get this to go with it for a tiny charger with voltage display, i have some on order

3

Thanks for the links.

So can I just simply wire it in on the charging tabs or is there a way it is suppose to be done. Do you know the current draw of that voltage tester you linked?

I guess ideally I’d want a tester that goes from slightly below 3V to slightly above 4.2V that has low current draw so that it doesn’t drain the battery after the charge cycle is finished.

4

I haven’t actually measured the current draw because i usually keep a watch on charging batteries but i’m sure it can’t be much, maybe someone else knows here.

I just soldered wires to the the charger outputs as far as i can remember, seems to work well.

Unplugged from power source it gives battery voltage, plugged in it gives charging voltage which raises incrementally during the charge.

I’m no expert on this so maybe someone else has a better way…

5

Alright thanks, we’ll see what others have to say. I also don’t leave batteries unattended but sometimes I don’t notice that they finish and they sit there for awhile charged.

I assume charging voltages correlate closely to the batteries state of charge?

6

I’m not the man to be asking about that, i just like experimenting with stuff. lol

Edit: Here’s the thread where i got the idea from

7

Alright, hopefully someone who knows will chime in. It would be nice to simply mod my charger to have the voltage features of a vp1.

8

If you go with the FastTech voltmeter better to choose red or green over blue for 0.2 V range (3-30V vs. 3.2-30V).

After seeing these results with similar LiPo meter from FastTech (1S-8S) I would confirm with a multimeter especially if only measuring one cell.

You can measure the internal resistance of the voltmeter too. If in doubt best to not hardwire without a switch to prevent unnecessary loading.

This might be of interest: