2LikesLiHV for offroad stock racing
09-17-2019, 05:18 AM
#1
LiHV for offroad stock racing
Hi guys, it's been a while no one asked about the LiVH, thought I would be the one to start it up.
For the hardcore 1/10 2wd stock offroad racers using shorties, is the LiVH recommended? I'm racing on astro... I thought in since I'm getting new batteries, I would go with the LiVH. If I got my voltages right, LiHVs are meant to be charged up to 4.35/cell, which is not allowed by roar. So what is real benefit of paying more for a LiHV if you are not charging to max capacity? I understand that some racers were already charging normal 7.4V batteries up to 4.35/cell, is the LiHV just a safer way of doing so? I don't plan to exceed 8.40 max charge, so I'm not seeing an advantage here. Should I just get a good quality 7.4v battery instead (Any Intellect variation or Sunpadow comes to mind).
I should add that the places I race don't tech the cars, so there's a chance that someone is charging up to 4.35.
Also as an additional question for LiVH, would you recommend either a 4100mah LCG or the 4900mah? I noticed people tend to use lower mahs for astro racing, but I read that LiVHs don't always reach the mah rating when fully charged to 8.40.
Thanks for any input
For the hardcore 1/10 2wd stock offroad racers using shorties, is the LiVH recommended? I'm racing on astro... I thought in since I'm getting new batteries, I would go with the LiVH. If I got my voltages right, LiHVs are meant to be charged up to 4.35/cell, which is not allowed by roar. So what is real benefit of paying more for a LiHV if you are not charging to max capacity? I understand that some racers were already charging normal 7.4V batteries up to 4.35/cell, is the LiHV just a safer way of doing so? I don't plan to exceed 8.40 max charge, so I'm not seeing an advantage here. Should I just get a good quality 7.4v battery instead (Any Intellect variation or Sunpadow comes to mind).
I should add that the places I race don't tech the cars, so there's a chance that someone is charging up to 4.35.
Also as an additional question for LiVH, would you recommend either a 4100mah LCG or the 4900mah? I noticed people tend to use lower mahs for astro racing, but I read that LiVHs don't always reach the mah rating when fully charged to 8.40.
Thanks for any input
09-17-2019, 06:07 AM
#2
Does your track check your battery voltage before you race?
09-17-2019, 06:12 AM
#3
09-17-2019, 07:38 AM
#4
You can charge an HV pack to 8.4v and it won't damage it. The chemistry is different in an HV pack, so the battery is designed to go to 8.7v. I like the lightest battery I can get. It lets you tune with weight, and have a light car. I only use about 1200mah over a race on high grip dirt and clay. I know you will probably use a little more on astro. The first lcg shorty pack was 2800mah and I had no problems making race length. My current pack is a 4000mah HV shorty.
09-17-2019, 07:43 AM
#5
Do you want to play fair or do you want to cheat?
If 4.2 is mandatory I would play safe in case they do a before voltage check.
Keep in mind that LiHV batteries charged on LiPo setting will not get the full capacity, that can go about 80%.
Otherwise charging LiPo in LiHV setting it is playing with your life because a bad cell can get unstable with 4.35v voltage.
If 4.2 is mandatory I would play safe in case they do a before voltage check.
Keep in mind that LiHV batteries charged on LiPo setting will not get the full capacity, that can go about 80%.
Otherwise charging LiPo in LiHV setting it is playing with your life because a bad cell can get unstable with 4.35v voltage.
09-17-2019, 08:11 AM
#6
Do you want to play fair or do you want to cheat?
If 4.2 is mandatory I would play safe in case they do a before voltage check.
Keep in mind that LiHV batteries charged on LiPo setting will not get the full capacity, that can go about 80%.
Otherwise charging LiPo in LiHV setting it is playing with your life because a bad cell can get unstable with 4.35v voltage.
If 4.2 is mandatory I would play safe in case they do a before voltage check.
Keep in mind that LiHV batteries charged on LiPo setting will not get the full capacity, that can go about 80%.
Otherwise charging LiPo in LiHV setting it is playing with your life because a bad cell can get unstable with 4.35v voltage.
Reading more about it, Fantom had a note saying that LiHV charged at 8.40 are not going to perform as a LiPo charged at 8.40. So there's really no reason to buy a LiHV unless planning to charge to 8.7.
And I agree 100%, I would never overcharge a LiPo to LiHV voltage, too scared of hurting me or someone around me. Also don't do the 40c, charge/discharge... maybe it's time to try mod
09-17-2019, 09:03 AM
#7
My local track doesn't tech for anything except that your motor is the correct turn. Roar rules are not enforced for anything except roar races. I run an outlaw motor and charge to 8.7v+ You have to be an extremely good driver to take advantage of the extra power. If you get motored in a spec class it is likely because you were slower through the corner before the straight, not because you lack power.
09-18-2019, 06:04 AM
#8
Main reason why you want a LiHV pack is to increase the durability so the pack handle higher charge rates and higher voltages depending on which charger you use.
A good race director will perform a tech inspection, at our club they only tech the A Main guys during the round before the race, normally 8.41+ has failed inspection.
If you are using an iCharger series, it performs an "over volting method" even though the end of the charge cycle will be close to 8.4V, most folks need to actually set the cell cutoff to 4.22V in order to get the actual end voltage to 8.40V.... most chargers I see typically top around 8.36V for tech.
Not all brands of batteries are equal, but in addition to over volting, you can significantly reduce your IR (also called "IR Boosting") when you dump the pack @40A discharge and immediately charge it back up at 40A just before you hit tech... timing is important, usually takes about 15 min to perform both actions... if you do it too soon ( like an hour before your race) then you won't get the full benefit.
IR Boosting is also illegal per ROAR rules (supposed to charge at 1C) but not typically enforced so it has been widely accepted at most clubs I've raced at.
If you buy a budget LiHV pack, expect it to last about 6 months before you start to see performance degrade where most brands of budget cells I have bought tend to start around 3mΩ when new and first signs of loss of performance around 8mΩ.
If you buy a quality LiHV pack, you can expect it to last around a year before 8mΩ and when new they typically read less than 1mΩ... not uncommon to get IR readings around 0.3mΩ when you are IR Boosting.
A good race director will perform a tech inspection, at our club they only tech the A Main guys during the round before the race, normally 8.41+ has failed inspection.
If you are using an iCharger series, it performs an "over volting method" even though the end of the charge cycle will be close to 8.4V, most folks need to actually set the cell cutoff to 4.22V in order to get the actual end voltage to 8.40V.... most chargers I see typically top around 8.36V for tech.
Not all brands of batteries are equal, but in addition to over volting, you can significantly reduce your IR (also called "IR Boosting") when you dump the pack @40A discharge and immediately charge it back up at 40A just before you hit tech... timing is important, usually takes about 15 min to perform both actions... if you do it too soon ( like an hour before your race) then you won't get the full benefit.
IR Boosting is also illegal per ROAR rules (supposed to charge at 1C) but not typically enforced so it has been widely accepted at most clubs I've raced at.
If you buy a budget LiHV pack, expect it to last about 6 months before you start to see performance degrade where most brands of budget cells I have bought tend to start around 3mΩ when new and first signs of loss of performance around 8mΩ.
If you buy a quality LiHV pack, you can expect it to last around a year before 8mΩ and when new they typically read less than 1mΩ... not uncommon to get IR readings around 0.3mΩ when you are IR Boosting.
09-18-2019, 11:09 AM
#9
Ive used a lihv 2 cell when allowed in my sct 4x4 and have found the slight added voltage you get was great for me.. and if you can get away with it use a full charge as in voltage on the lihv..
and you will never get away with the high amp discharge charge cycling that was mentioned . the pack will be to hot and fail tech inspection...all my chargers when set to lipo a cell comes off charger at 4.20 volts never 4.18...
and you will never get away with the high amp discharge charge cycling that was mentioned . the pack will be to hot and fail tech inspection...all my chargers when set to lipo a cell comes off charger at 4.20 volts never 4.18...
09-18-2019, 10:24 PM
#10
Some of the low quality chargers I have used in the past might sometimes get close to 8.40V, but they often tend to be very unreliable, while they might read 8.40V on the display, they typically read closer to 8.36V after hitting tech, voltage tends to drop where a high quality charger does a better job of "conditioning" the cells to remain at 8.40V for a longer period than what a budget charger can do.
Here's a couple pics to see the 4.22V over volt trick in action (Green Port#2 on the right):
Notice how the average voltage peak is at 8.479V, this is how the charger "conditions" the battery to hold voltage at 8.40V at rest:
Main difference is this charger brings the voltage above the desired end voltage while keeping amps up, where a budget charger drops amps very quickly and tapers the voltage so it barely hits 8.40V and then the battery quickly drops voltage to 8.36V when you go to tech
Although the end voltage reads 8.409V which in theory would round up the voltage to 8.41V, but it typically reads 8.40V at tech once you power up the ESC to show it in blinky mode, sometimes a quick blip of the throttle might be necessary.
Here's a couple pics to see the 4.22V over volt trick in action (Green Port#2 on the right):
Notice how the average voltage peak is at 8.479V, this is how the charger "conditions" the battery to hold voltage at 8.40V at rest:
Main difference is this charger brings the voltage above the desired end voltage while keeping amps up, where a budget charger drops amps very quickly and tapers the voltage so it barely hits 8.40V and then the battery quickly drops voltage to 8.36V when you go to tech
Although the end voltage reads 8.409V which in theory would round up the voltage to 8.41V, but it typically reads 8.40V at tech once you power up the ESC to show it in blinky mode, sometimes a quick blip of the throttle might be necessary.
Last edited by billdelong; 09-18-2019 at 10:36 PM.
09-30-2019, 06:03 PM
#11
Tech Apprentice
My local track MAY only tech voltage at a big race. Last big race I had to burp the throttle a couple times to get my newish SMC pack to pass (standard 7.4 non Hv, charged on a cheap charger). I know guys are fully charging their HV batteries (not really much can be done about it. Hard enough to get the race day to go smooth without teching everyone before every race). I only charge at 1c and noticed my maybe 7 month old packs are losing some power towards the end of the run. Figuring it's time for fresh packs and use current packs for practice.. I'm not really a if you cant beat them join them type. In stock racing at my club you are 1 or 2 wrecks from finishing 1st , mid pack or maybe last.
09-30-2019, 07:22 PM
#12
I’m sure that in a few years as regular LiPo’s get phased out and LiHV’s are the only batteries on the market, the sanctioning bodies will probably bump allowable voltages to 8.7V... After all, batteries eventually outlive their usefulness, and you have to keep buying new ones when they do, right?
In the meantime, just charge by the rules, and make sure you buy batteries with just a little more capacity to make sure you have enough juice as mentioned above.
It was nice to see everyone helpful - I’m in the process of buying equipment to get back in the hobby, and when I asked the same question regarding how they verify a few months ago, I was accused of wanting to cheat for asking just two or three posts in...
In the meantime, just charge by the rules, and make sure you buy batteries with just a little more capacity to make sure you have enough juice as mentioned above.
It was nice to see everyone helpful - I’m in the process of buying equipment to get back in the hobby, and when I asked the same question regarding how they verify a few months ago, I was accused of wanting to cheat for asking just two or three posts in...
10-01-2019, 08:11 AM
#13
Outdoors anything goes. At my nearest popular large indoor off road track, there's dischargers in at least 1/3 of the pit spots. If lipo bags are mandatory, then I push my cells. Only onroad seems to be taking it easy on charging.
One hard cycle every once in a while to get a good IR check on the battery. Seems like cycled batteries perform well for longer. 6-12 months. My gently cared for batteries last just as long, but performance drops off sooner in life.
One hard cycle every once in a while to get a good IR check on the battery. Seems like cycled batteries perform well for longer. 6-12 months. My gently cared for batteries last just as long, but performance drops off sooner in life.
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